Not everyone is fit to be a parent and as such, unfit parents should not be allowed to have children. Unfit children have their children taken away from them all the time, and this is normally considered a necessity. Adoption requires an approval process, sperm donation requires an even more rigorous approval process, why isn't there an approval process for normal procreation?
If you admit that you would not let just anyone baby sit your kids, then you admit that not everyone is fit to be a parent. If you admit that not everyone is fit to be a parent, then you agree that some people should not be allowed to have children.
Everyone says "Everyone is equal", but in reality, some humans are genetically superior (more intelligent) to other humans. Darwin's theory of evolution states that the genetically superior members (the ones with traits best suited to survive in their environment)of a species are more likely to survive and carry on their superior traits to their offspring. Inferior members of a species (the ones with less desirable traits) are less likely to survive and reproduce. But now, we humans have messed up that system, providing the neccessities of life (food and shelter) to those who do not deserve it (the inferiors). This way, we allow inferior (less intelligent) people to reproduce, passing on bad traits to their offspring. But, this can be fixed. By forbidding inferior humans to reproduce, their inferior traits will be eradicated from the gene pool, allowing humans to become, as a whole, better. Therefore, some people should be prevented from reproducing.
World population has been increasing EXPONENTIALLY throughout the years and decades human civilization has lived in. As our world and society advances through technology, better health care, and other discoveries, so will the number of people living in it 7 billion people is not at all a small number, and it is growing. It's plain from sight that Earth teetering on its human carrying capacity, and that capacity may soon be or already be crossed and our race will suffer the consequences such as food shortages, wars over limited resources, lots and lots of death, extinction of varieties of the other organisms that inhabit the world alongside us, extreme air and other environmental pollution, and who knows what else. We have been desperate to try numerous ways to limit the population such as spreading awareness and educating others about the matter or adopting instead of conceiving, and China had also imposed a one-child policy (which does have its own set of consequences) in order to calm its population chaos. Preventing some people from having children can also be considered another way to help fix the crisis. We can look through records of adults, like their medical and criminal records, to see if they would bear healthy children they would most likely take care of well. People who have a family history of having diseases and other conditions should be prevented from conceiving for the sake of their children and the world, and so should people who have a record for committing crimes such as rape, domestic/child abuse, and murder. It's understood that limiting people from conceiving can be invading their human rights, but these people should first assume responsibility and think about their world and what kind of a future their child could be plunged into before they conceive for personal reasons like just for the sake of reproducing with a significant other and seeing the result.
Some individuals were not the best raised by their parents and are not in a mental state to be responsible enough to mentor to another life. Some have so much mental and medical issues that the likelihood of our child child being worst off than them will increase. No way
As much as I would like to say everyone is fit to be a parent, that simply is not the case. For example I have an aunt, who is now in rehab for the fourth or fifth time in her life. She had two kids, and abused them. She was an alcoholic and did drugs, then when she got her kids nothing changed, except she would steal their money to buy drugs or alcohol. Some people don't change, and some people don't deserve the right to be a parent, it is unfair towards the children. Anyone who has ever abused their children, or treated them with complete and utter disrespect does not deserve that right.
Apart from the massive human rights abuse, it is wrong. Everyone must be allowed to have children, and the big decision is in the hands of the parents, not the government! Who would decide? Who should have the choice of deciding whether someone should be able to reproduce? Obviously, if someone is mentally ill, then they shouldn't. But it is their decision, and there are many agencies set up to help people like this, and advise them what to do. FREEDOM TO ALL!
...KEEPING them is an entirely different issue.
There are some people who are just unfit to parent. They should get due process and everything but if someone has a certain record they should be required to hand over their kid right after giving birth. It should take particularly serious offenses for a permanent bar to keeping your own kids. In particularly no one convicted of malicious child abuse should get to keep new kids they have.
As for genetics science and technology are getting better. We are on the verge of freeing ourselves from natural selection and being able to treat and cure all manner of disease. It will take a while, maybe even centuries to really get the science down since changing one gene will change more than one thing so ultimately brand new genes will be necessary for allow certain improvements without drawbacks. BUT give it time and the full interactions will be worked out. In the short term we'll probably just find some cures for diseases (SCID trials in gene therapy are already showing great promise). In the very long term scientists will figure out how to safely and effectively enhance human beings.
Avoiding the inhumanity and barbarity of forced sterilization is worth patiently waiting for scientific and technological advancement.
So if a poor couple want to have babies that they most likely can't provide for, It's your choice. But in my OPINION, I wouldn't do it. If you are an incest couple(parent/child, siblings, grand parent/grand child, uncle/niece, etc.) I'm not saying you can't have a baby, and I won't force you not to. But looking at the facts, I would recommend not inbreeding.