There are a lot of reasons to defend cousin marriage, and most of them are kind of boring and normie-morality-ful, but the scalding hot Galaxy Brain take is also correct:
If a high rate of birth defects is the price of creating a sub-population that has all the substantial benefits that accrue to Ashkenazi Jews today, it is definitely worth it.
People seem very confused about how to interpret this. So I’ll clarify:
I’m “trolling” here in the sense that this is an unnecessarily weird, controversial, third-or-fourth-order-effect-oriented response to an issue that should rightly be dominated by considering basic first-order moral/political/cultural effects. That’s what I mean when I call it a “galaxy brain take.”
But it’s not, like, wrong on its own merits.
In particular – one of the things people say all the time about cousin marriage is “oh noes, the genetic effects!” Even @mitigatedchaos, who has problems with cousin marriage that are much more substantive and subtle, resorts to that one as a rhetorical bludgeon. So it’s worth providing a reminder, if perhaps a bit tongue-in-cheekily, that the genetic effects of inbreeding aren’t necessarily bad; pretty much every intentional animal-breeding program, and every unintentional-but-ultimately-valuable human-breeding program, relies heavily on inbreeding; the ultimate valence all depends on what it is that you’re breeding for.
Ashkenazi Jews…my own people, for whatever that’s worth in this discourse hellpit…aren’t particularly known for cousin marriage now, but it was vastly more prevalent up through early modernity. Which is not surprising when you consider how many unusual defects and disorders are super-prevalent in that community (Tay-Sachs, etc.). And, well, given how it all shook out, that doesn’t seem very regrettable.
In general, even when I’m trolling, I’m doing so with enough earnestness that I’ll stand by the points I make (with greater seriousness and less fun, if need be).