A rational person will likely abide by the law and be kind to others such as not being racist because he would most likely believe that all humans are made up of atoms and that race has nothing to do with their personality or characteristics. It would also lessen the divide in the society as everyone agrees that there is no god and therefore do not have to fight or argue with each other on the existence of god.
Morals come from the ability of empathy that we have developed. If religion went away there would be less people acting off of the radical "morals" in "holy books" (example is hate for gays). If everyone was an atheist there would be morals AND rational thinking, allowing for an improvement to the ethics of society.
Many religious denominations encourage their followers to pray for healing and to cure diseases instead of, not in addition to, receiving proper medical treatment that has been shown to work. This harms anyone who has to suffer because they or their family refuse to properly medicate. Additionally, some sects handle untamed snakes because they believe that God will protect them from any harm via the snakebite. Even after long hospital trips and horrible wounds, many members will still voluntarily allow themselves to be bitten by snakes on the basis of their faith alone. Religion isn't just a belief people have, it's a mindset. A mindset that makes people do things that harm themselves and others.
The ethics of our modern 21st century society is vastly superior to that of the most pious, progressive societies of 100 years ago. There's a reason for that: Ethics and Morality evolves.
This is totally unlike the stagnant, totalitarian dictates of the autonomous, unanswerable authority claimed by religion, a claim for which it has NEVER produced a shred of evidence.
The ethics of a modern society, in order to be relevant, must be constantly reevaluated, reasoned, argued, discussed, debated, and ultimately intelligently designed. They cannot be set in stone or immovable once enacted, they must always be subject to question and debate.
This CANNOT occur under the supervision or proxy authority of an unelected, unassailable, totalitarian divine overseer.
Back in the biblical ages, religion was needed. People were murdering and raping each other and could not be stopped in any way except by making them feel bad about themselves (i.E. They'll go to hell). But in today's society, with reasonable laws that are enforceable, as well as the ability to teach children right and wrong without a deity, we can remove the social training wheels known as religion and live in a harmonious Humanist society, theoretically.
You see ethical behavior in animals just as you see unethical behavior. You do not need a book telling you what to do, unless that book is the code of laws of the country that has determined something is wrong. Also, if you do need a book to tell you how to act, you probably need to get a set of balls and stop blaming a book for bad decisions.
I'm a moral person. I spend a lot of time and energy helping those struggling with depression, I encourage the best in my friends and family, and I'd say I'm accepting of many, regardless of who they are. Now, I will confess that I draw my morals from my rationality, but I don't see how that is any less valuable than those who draw their morals blindly from the predetermined set in ancient text. So to say that without religion we would all be immoral is simply false. If anything, rational morals are much more beneficial because they are capable of changing with the world. Gay rights has been a major struggle for about ten years, because religious minds were so set in their ways that they opposed the very suggestion of an alternate course. I'm willing to bet rational thinkers didn't feel nearly as opposed to this freedom. We need to be able to grow and evolve without stalemate, hate, or even a strong easily offended bias. While religion had it's place many many years ago, it no longer leads our society forward, and the cons of war and infighting still follow it. If our world were full of those who drew their morals from their rationality and their goals from thought, I think our outlook would be much more conductive to our own success.
Even if religion did nothing to improve morality (an untrue statement, by the way), it doesn't harm morality (except when it incites holy war or something). Therefore, its elimination would not make society more moral and it'd probably make society less moral. This last sentence is just being added so that I have enough words.
The laws that we have today came first from religion. Religion gets people to think view a emotional view toward another being. Laws did not come from a simple rational thinker. Without the religious law we would not have any moral since, with no religion people will easily put moral a price on life. Meaning the whole thy shall not kill thing, would be like, thy shall kill if reason found suitable for once peace.
One of the biggest problems of our society today is the great debate over religions and their questionable practices. While I can't say that religious people have always been innocent, I will say that there is at least a decent standard when it comes to morality. Most atheists I've seen have terrible personalities and tend to look down on people who believe in hope for the world that we live in. When you stop believing in God, you start believing in yourself than next thing you know your stealing, lying, cheating, and than you'll start hurting people. Than you start murdering people. Next thing you know where dropping an atomic bomb on Japan. I can go on and on but basically these atheists can be such horrible people. At least with religion you have guidance.
I'm truly wondering, how could it? Think about it. The law you're under is subjective in a way. If you live in the US, there are many rules, obviously, but let's take murder as just an example. Murdering in most cases is wrong here. But let's say you move to a different country where murdering is okay. What would stop you from murdering someone if you had the desire to? If it's okay in the new country you live in, why not?
This isn't to say atheists can't be moral. I'm not saying that at all, so don't jump to conclusion. I know atheists aren't all horrible people who go out and kill and rape and what have you, but I'm truly wondering, what keeps you from doing something wrong? What /is/ wrong in your case? As a Christian, I have laws placed upon me from God, but as an atheist, if you truly were in a country that allowed rape or murder or what ever else, what would be keeping you from doing so if you ever had the desire to?
Also, I realize I kind of avoided the question, so, to give a quick answer before I run out of space: If everyone became a non-believer, I'm assuming of God, I don't think it would make much of a difference. This question seems to be similar to the one I've answered before about if Christians are the cause of most of the problems in our society. Yeah, there are bad Christians who aren't actually Christians, but people that have labeled themselves as such and preach hate. But that doesn't mean there are enough of them to say, if they were wiped out and atheism was everyone's, for lack of better word, belief, that society would suddenly be better off. We /would/ be better off without the "Christians" preaching hate, but I don't think society would somehow improve just because everyone stopped believing in God (or any other deity for that matter).
Mao, Pol Pot, Stalin, Khrushkev, blah blah blah, all psychopathic, murdering dictators. They killed people because they were religious. If atheists were any more than 0.4% of the population they would do the same thing owing to their smug sense of superiority over everyone else. Atheism is one step down the road to nihilism.
Philosopher Simone de Beauvoir said once said that without religion, there would be a greater need for ethics. While the institution of religion has questionable components, society does not need to eliminate it completely. However, morality should remain secular. I greatly dislike it when people use religion as a moral justification.
Look at Cuba. For 50 years under Castro, atheism was IMPOSED on their society. And look what that did---it created moral confusion, and a horrendously un-free society.
Atheism creates a society where all morals/ethics are subjective to each individual. (the ends justifies the means) (Cuba)
Religion (more specifically Christianity) created the most free, enjoyable nation on earth to EVER exist: the United States. It was founded upon Judeo-Christian principles by men who understood a Christian worldview of government.
Thousands of years ago people blamed the gods for poor harvests, for thunder and lightning, in fact, for almost everything that people could not explain. With the advances of modern science, we have more and more explanations for what were previously inexplicable except by 'god'. Today, science has advanced so far that we have reasoning and explanation for almost everything. That is, except for two questions - what happens when we die and why are we here? These are where people still hold out for god, the unknown, the inexplicable. If ever science finds an answer to these questions then the whole concept of god will truly become redundant and we will all become non-believers. In a way, if we did ever find those answers, we would essentially all have become god himself.
Because religious people feel that religion is the only reason people have a moral code, it can be logically deduced that the only reason they have a moral code is because of their religion. If we took religion away from the religious, it would be like taking medication away from the criminally insane.
I can further back up my claim that the religious have less morals by statistics. In the U.S. about 75% of the people are Christian. It is no surprise that about 75% of prison population is also Christian. Atheists are about 2% of the U.S. population yet they are only about 0.2% of prison population. The other religions are also about equal in both populations. This means that the religious are 10 times more likely to commit a crime than an atheist. Maybe it is because they feel they can just pray for forgiveness and everything will be okay. Could also be that some may commit a crime in the name of their god. Let's keep religion legal so the religious don't go around end up with no moral code.
I'm an atheist, and therefore I obviously don't believe that one needs God -- or the idea of God -- in order to be moral. But I also don't believe that there is one-size-fits-all rule in favor of other side, and we ought to examine this issue on a case-by-case basis: that is, we admit that there are good people in both camps, and religion does not inherently affect personal morality for either the good or the bad. People attempting to make the case for religious oppression are missing the point: most religious use birth control, most believe in same-sex marriage, most have reasonable outlooks on the world and don't believe in a literal interpretation of the Bible, et al. Insofar as we're not speaking about fanaticism -- the type that sparked wars for centuries -- I don't think we can make the case that religious is inherently harmful to society. Then again, we also cannot say that it is the determinant of morality, for surely it is not.