This isn’t a slippery slope.

Your starting point, where it’s a good idea to socially pressure people to not reproduce based on your assessment of what traits are sufficiently undesirable, is already bad.

We don’t have to slide anywhere.

“My assessment” is kind of uncharitable. Again I’d take huntingtons as an easy example of something that consigns one’s children to an early and horrible death. Not to mention in a society where we often bear the cost of medical care, social pressures are inevitable and more justified.

Why do you think it’s bad? This is a strong opinion weakly held for me; I recognize it’s controversial but fail to see why it’s not an obvious choice.