The diseases you mention, things that cause imminent death are cases where I do agree that genetic manipulation should be allowed.
Things like schizophrenia run in families, yes, but consider the fact that the families with the disease are still alive today, having not been killed off due to one reason or another. I'm positive that in order to get rid of the disease, you have to get rid of the benefits that the genes that cause that disease also lead to.
The problem is that genetics is complex, it is something we understand in theory, but rarely do we know the full implication of changing a person's DNA. Making people all big, strong, losing weight fast, and so on, may seem appealing, but there is a good reason that people who don't do those things are still alive, even if we don't know that reason yet.
We need to keep that attitude, the idea that all bad things are good, and good things bad, when it comes to human biology and traits. I would never be who I am today if it weren't for my negatives, so to talk about how great it would be if my parents did something to change me as a child is akin to talking about suicide.
And I agree that we shouldn't accept parent's doing things like drinking, smoking, or otherwise, if they plan to have kids. Those who do that sort of thing are bad people, no doubt about it.
Why can't you fuck them up like this too? What makes genes so different,
The former is indirect, and often the way people were just acting.
The latter is an explicit attempt to equalize, normalize, and generally cleanse humanity of traits that humanity deems negative.
Nature, however, has different ideas of negative and positive, and that's the problem. The way people act naturally, the diseases and issues with our genetics, have been around for billions of years, they are a part of our species, and likely have all played some role in helping humanity survive.
I have chosen to believe that individual human lives are valuable, and valuable enough that illness should be prevented when possible.
Human lives only hold a value greater than the lives of any other creature because we a part of a larger system that values us. Without that system, without our ability to be a part of society, we are no better, or more important, than a pig, a cow, or an insect.
Where is it written that genius requires physical suffering and deep social ostracization?
Physical traits are often linked to genes. Genes often create multiple physical traits, and often being good at one thing requires a sacrifice for another. Hawking is a bad example, because his body and mind are likely effected by different genes, but my point is that, when selecting for good traits, we will also be selecting against great ones.
Being greater than others requires being different. Being different implies you will be picked on, bullied, and so on. It's not that being picked on results in genius, but the other way around.
By your logic we should ban vaccinations because FDR had polio
Vaccinations are not changing the very genetic code of who we are. Humanity has had the tools with which to change our genetics from the very beginning, in the form of eugenics. We saw how that failed, this will go along the same route.