I'm going to be one of the very few to say yes to this. To erect a monument with the purpose of expressing disbelief in a God, I think it is very contradictory to American culture. As at 2012 80% of American's claimed to be Christians and their traditions reflected Christian principles.
During a presidential inauguration ceremony it is stated "For I have sworn before you and Almighty God the same solemn oath our forebears prescribed nearly a century and three quarters ago".
On a US one Dollar bill it clearly states "In God we trust", In a US court of law you swear before before the Bible - God that what you say is truth, these are but a few examples of many. The point I wish to make is whilst America was a secular nation under a constitution derived from man, they were still a heavy influenced nation that submitted its social and political governance to godly beliefs.
To allow the construction of any monument that represents disbelief in a God in a country that traditionally prides itself on their forefathers works is 'disrespectful' to its founders that originally held godly beliefs and to America, the great nation they established.
Unlike an agnostic, an atheist makes a point not to accept God, ironically recognizing the God to say so. An Agnostic simply does not recognize religion, any religion.. To have a monument in this situation is not illegal in the US. Let's not get this confused with disrespect. The whole premise is to denounce a God of another, which by definition is antagonistic and therefore disrespectful.
Religion does not belong in the public sphere in a modern democracy, only in the private sphere of the individual. Furthermore, your constitution has an explicit ban on supporting any specific religion, so if any christian monuments are built on public sector premises then any organization must be allowed to put monuments there. This could in general get impractical, so the best solution would be to just refrain from building christian monuments (or any other controversial symbol) in the first place.
America is not a Christian nation. It is a nation based on freedom and progress. The monument is simply etched with notable quotes from wise men and women. How is that disrespectful to America? Of course, no one says anything about it's neighbouring Christian monument being disrespectful, I think that this is an absurd question.
Burning the American flag may be disrespectful to America, for instance, but we are not a theocracy, so being disrespectful to religion has nothing to do with being disrespectful to America. Quite the contrary: We are a pluralistic nation founded on Enlightenment ideals (not Christian) as well as freedom of expression.
Our government, by the Constitution, cannot endorse or establish a religion. Therefore if a religious monument is placed on government property, they have to either allow ALL religious positions to equally place such monuments or ban them altogether.
The fact that the American Atheists organization exercised their constitutional right to place a monument there is in the spirit of America, not disrespectful of it. Too many Christians in this nation have the mistaken notion that this is a Christian country or that the mere fact that atheists exist is somehow disrespectful.
The monument originally came from a lawsuit stemming from American Atheists over a ten Commandments monument posted outside a county courthouse in Florida. This would have been an easy case for American Atheists to win as there are countless other precedent cases that have resulted in a favorable ruling for them. The county realized this, and entered mediation with AA. The county had two choices: take the monument down, and ban monuments all together, or leave it up and open the area up for everyone to put a monument up. They chose the latter option, thinking no one else would put anything up. American Atheists called their bluff and decided to put up the monument that exists there today to remind citizens about the secular founding of our nation. So, in essence, it is not disrespectful, because, as Barack Obama said in his address to the UN concerning "The Innocence of Muslims," "I know there are some who ask why we don’t just ban such a video. The answer is enshrined in our laws: our Constitution protects the right to practice free speech. Here in the United States, countless publications provoke offense. Like me, the majority of Americans are Christian, and yet we do not ban blasphemy against our most sacred beliefs...Moreover, as President of our country, and Commander-in-Chief of our military, I accept that people are going to call me awful things every day, and I will always defend their right to do so. Americans have fought and died around the globe to protect the right of all people to express their views — even views that we disagree with...We do so not because we support hateful speech, but because our Founders understood that without such protections, the capacity of each individual to express their own views, and practice their own faith, may be threatened. We do so because in a diverse society, efforts to restrict speech can become a tool to silence critics, or oppress minorities. We do so because given the power of faith in our lives, and the passion that religious differences can inflame, the strongest weapon against hateful speech is not repression, it is more speech — the voices of tolerance that rally against bigotry and blasphemy, and lift up the values of understanding and mutual respect." The monument is not disrespectful at all; instead, it is a testament to free speech.
In the construction of a monument it is believed by the architects to be beneficial. It is by the architects that the monument is dreamed and made real. However. Because a belief cannot be held as being fact, the architects cannot be held as being considerate of others. Is it then beneficial to erect a monument in honor of what people believe?
Every spiritual belief (or lack thereof) should be allowed to be represented with a monument if they so desire. It does seem a little cheeky of them to specifically make the monument to atheism, rather than to humanism or to mankind in general though. I say well done. Those who think that only their beliefs or views should be represented need to be reminded that this country is supposed to hold all beliefs as equal.
I'm not an American but see it from this view: If it was a religious monument and people questioned if it was disrespectful towards atheists, there would be a huge explosion of people saying that they have the right to honour their religion. In a way, atheism is a religion, a belief in science, or simply that there isn't any gods. So why can't we voice our own views when other religions so often voice their own?
America is a secular country and allows freedom of belief and religion, although atheism is not a religion it is still a concept or collection of beliefs that people follow, having this monument offend anyone is like having a monument of any other religion offend someone. Although America has a profoundly Christian population it does not enforce Christianity on anyone leaving people to believe what they wish and make monuments as they wish.
If Christians are free to express their thoughts and opinions on a higher power than others of countless religions should be able to partake in the daily culture of America. This country says it has a separate church and state but it sure doesn't act like it. The government implements the Christian life style onto all, including many who don't want to or are not interested in partaking in their Christian life style.
All people of all religions should be able to express themselves as much as Christians are able to in America. It's called freedom of speech, people.