In his latest article he explicitly and approvingly cites Marx twice (with a few more implicit mentions) and comes up with two elegant destructions of common billionaire apologia arguments: " They don't do it for the money - then it should be no problem if we tax most of it away, right?" and "They worked hard for it - well, thieves can also work hard".
Obviously he has a number of very shitty takes but it's over the top to dismiss him completely.
He's a left anticommunist, which is bad -- and I say that as someone who thinks he's doing good work overall. But if we cancelled every U.S. leftist who's stuck on Cold War propaganda about socialist states (even ones who've shown the willingness to disregard Cold War propaganda on other issues), we're not getting anywhere.
The approach for these people is critical support. Praise the good stuff they do. Call out the bad stuff without turning it into "this person is awful, fuck them and everything they've ever stood for, they get the wall." Challenge them on their bad takes in the way you'd challenge a friend on a bad take.