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.
"tankie" just means anyone to the left of bernie
No, no. Trust me, the guys this person are referring to are NOT to the left of Bernie.