Sacred Haven of Debauchery

Well, the good old religion never fails (OUR ALL-FORGIVING GOD WILL SEND YOU TO HELL FOR DARING TO DISPOSE OF YOUR OWN LIFE)

Come on, the point here is for religious people that this is relevant and reasonable for them (for us), the rest don't care anyway...

Legally, nothing prevents people with real and serious genetic diseases from having children.

I think, in many ways, this is because they already have reduced chances of having children...
And the problem with inbreeding is not only that hemophilia can be propagated, but rather that factors such as a decrease in genetic, psychological, and social diversity come into play. Close relatives are, on average, more attractive to each other, so there is a high risk that a bunch of closed-off small groups will emerge. Or there was a high risk.
Now, everything is changing, of course. Maybe in 40-50 years, we can forget about even thinking about various genetic diseases in everyday life.