system
Given the following post, respond as if you're commenting on Reddit:
human
I think that a system of eugenics is the only morally correct path for a society to take and that selective breeding to remove a variety of negative conditions from the human race should be enacted. CMV

People with genetic disorders, brain damage, mental retardation, allergies, natural predispositions to certain conditions (cancer, diabetes) or hereditary illnesses should not be able to have children because this creates a future in which these conditions are invariably worse and more prevalent. The especially unintelligent (cognitively-speaking) or naturally weak (physically) should also be prevented from breeding in order to nurture a smarter and stronger human race. I've always felt this way and though that (in this sense only) Hitler was right to want to further human advancement through artificial selection.
gpt
Point of order: Brain damage is not heritable, so unless you want to misrepresent your position as "kill all the freaks," I'd eliminate that one from your list.

When you get into eugenics, how do you decide who is and isn't allowed to reproduce? If you eliminated everyone who wasn't perfectly healthy, very strong, and very intelligent, you'd lose a ton of genetic diversity, which makes your new population extremely vulnerable, not to mention the problems with a sudden drop in population. If you do this with the entire human race, you could put the species at risk to extinction. So instead, you have to let some people by, maybe people with less serious problems. So now you have to draw a line. Are you going to let the nearsighted people and people with seasonal allergies have children, but let the asthmatics die off? Okay, here's a guy with asthma, otherwise in pretty good shape, chemical engineer, but he's married to a bestselling author with an IQ more than two standard deviations above the mean. If he can't have kids, odds are she won't either. Forcing her to get pregnant by a male of your choosing seems a little dystopian even for you, so you decide that rules are rules, and the husband can't have kids. It's a good thing you're available to make all of these case-by-case decisions yourself. Of course, you couldn't, in reality, so you hire some representatives to help make these tough calls. Better hope that none of them will accept bribes or fake medical records from rich people who would otherwise be disqualified. Who knows how much people would be willing to bribe one of your officials for the chance to watch their child grow up? 

Meanwhile, that author from earlier has devoted all of her time, energy, and considerable resources to editorializing on the callousness of eugenics. People are getting pretty dissatisfied. But if you're in total control of everyone's reproductive system, you can probably hush up one writer, right? Just tell her publisher that if he wants to ever have children, he'll stop publishing this stuff. 

Women start getting pregnant in protest. You haven't managed to survey everyone yet, so you don't know how many of these women should be allowed to be pregnant. So, what can you do? You can't just let them have their kid, or everyone will just start defying you. You'll have to detain these women while you sort out which ones you'll have to abort. Of course, none of them are telling you the truth about who the father is, so you have to do a lot of footwork to figure it out. Better get it done quick, before these ladies give birth. And at the end of the day, though, you still have a lot of fetuses that you can't pin down, so just to be safe, you abort them as well. You make a new rule: Everyone gets their tubes tied by default, and to get it un-done, you have to get approved. That author comes in right away to get her ligation reversed. Snip snap. But the reversal doesn't take. In fact, surgical error has rendered her unable to have children. She buys printing equipment on the black market and starts churning out anti-eugenics propaganda from a secret location. Well, you track her down in an abandoned subway station, but she's long gone by the time you get there, and what's more, she's booby-trapped the place. Five of your security force are killed, but you've got her on the run. Your security catches up to her, and she resists arrest violently, so they have no choice but to kill her. 

In the meantime, people have been getting their vasectomies reversed in back-room procedures. But you've got more to worry about than that, because it looks like you've created a martyr. A rebellion begins, and eventually overruns your security, provided none of the numerous assassination attempts succeeds. Revolutionaries storm your headquarters. Your only option is to retreat to your bunker, where you marry your mistress and dictate your will before your new bride chomps on a cyanide capsule and you shoot yourself.

TL;DR Improving the health/intelligence of humanity is a nice goal, but giving it teeth requires dystopian totalitarianism.