I am gradually updating in favour of the hypothesis that at least one of the admins either approves of mass-downvoting as a means of influencing LW culture,

The way Eliezer treated eridu, and (IIRC) asked that the upvote/downvote buttons be re-added to user overview pages provided their “% positive” was low enough, make me suspect that too.

or else has a strong enough dislike for the sort of ideas that appear to be be the targets of mass-downvoting at present that s/he considers the mass-downvoting to be a good thing.

I think it's unlikely that Eliezer dislikes progressive ideas about gender that much, and all but impossible that Alicorn does. (What other mods are there?)