[hrhdave]

Tay-Sachs screening is done before marriage. All Tay-Sachs trait carriers are descendants of a single 17th century Jewish ancestor. So in that respect, it is a matter of consanguinity.

[Romulus]

That's interesting, but using the same standard for consanguinity would have made human reproduction impossible in most communities throughout history, inlcluding today.

But as you point out, Tay-Sachs screening is done before marriage, so it's a bogus excuse for murdering your own children.