Jews who marry the same sex, will, in time whither from this Earth.
Biologically, they extinct themselves by definition.
True, but wouldn't that pertain regardless of whether "gay marriage" was legal or not? I'm not arguing for or against "gay marriage" with that rhetorical question,, but I don't see the relevance of your point to the "gay marriage" debate.
There can be no multiplication of their gene pool in a biological flow into the future. Their line basically stops right there, when they wed or live in union.
Of course they can adopt or do IVF (women) but technically speaking, what can be the byproduct of such a same-sex union...nothing at all, no kids and 2 dogs or a role-confused adopted or IVFed child.