Ohhhh, that's where that phrase came from.
There's a regular on MN who prides themselves on being contrarian and is therefore highly predictable (natch).
They're not notable as an original thinker, and did indeed spew out something about "beta men" recently – perhaps it was "alphas" could never vote for Harris because only "beta men" could vote for a woman? Sorry, not exact quote.
Anyway, along with "WTF?", my immediate thought was, "So whose message-stream have you been bathing in now?"
Not that I spend much time thinking about this poster, you understand, but they're a reliable... not so much canary, as parrot? And the bonkersness of the particular messaging struck me, so I wondered on the origin.
Looks like I've got the answer to that one now, thanks @Frowningprovidence .