Still tapdancing around the main point I see.
Completing the above paragraph (as well as quoting the original in its entirety; an innocent ommission, I'm sure) would highlight the nonsensical nature of what prompted my original response.
It is obvious to everyone that the most likely means of transmitting those genetic defects is through marriage, a reality you attempted to dismiss out of hand.
Your propagandistic appeal to universality notwithstanding ("It is obvious to everyone ..."), your premise is absurd on its face. How does marriage in any way constitute a more probable vector for the transmission of genetic defects than intercourse outside of marriage? Or are you so naive as to believe that the latter does not exist?
Furthermore, in your zeal to pursue your absurd line of reasoning, you've defeated your own argument. If indeed marriage is the principal vector for the transmission of genetic defects, that is the most powerful argument AGAINST the institution.
Whatever you do for a living, I hope you do it better than you argue.