The context to this is saying about how they're not a fan of the subreddit LeftWingMaleAdvocates, which is a bad subreddit, it's mostly just anti-feminist and basically just MRA, but they just call themselves left-wing. Most of their "left-wing" stuff is actually just "classical liberal" talking points, so they are bad, but calling them tankie is ridiculous.
Yeah I've had similar experiences, funny enough they would call Keith McHenry one of the founders of their org a tankie when he is very much not one, just has good takes on imperialism.\
(unfortunately he also has some antivaxx brainworms last I talked to him)