Point taken re: the structure of this 'industry' and this person's future employment. That said, the persona you present when posting publicly like that though... sort of screams 'I am difficult to work with'. Bad move, regardless of the industry you're in.
TT RPGs are a small industry.
Word-of-mouth about your behaviour is going to count for infinitely more than an angry Tweet directed at the industry equivalent of like, Omnicorp from Robocop. People hiring you will not be going on just what they've seen on Twitter, and I mean, if they are, oh boy, you probably don't want to be hired by them, even if all they've seen is positive.
Further, a lot of people have posted a lot of things that "scream" "difficult to work with" and continue to have careers across a variety of creative industries. You kind of have to be a serial offender and/or known to be a jerk in person for this to be a big problem (or at least attack some beloved studio, not an um, be-hated one). I mean, Chris Avellone, writer of Planescape: Torment and some other games regularly posted kind of wild blasts about his own employers and took pot-shots at them in semi-public for years and it wasn't until a sex assault scandal that that counted for anything. Conversely, Skyrim composer Jeremy Soule basically lost his career without making wacky public statements/insulting employers, and before a sex assault scandal (though there was one), because he was so erratic, demanding, and hard-to-work-with, despite being super-talented. The scandal was just a cherry on top (this is easy to see from looking at what he worked on).
I will say this might make people ask more questions about your behaviour, but so long as the answers they're going to get are positive, I don't think it'll have consequences.
I should stress I broadly agree with you that posting this isn't the best idea, especially for people in fields like mine! I literally don't post on Twitter, nor re-Tweet, and now likes are invisible there's absolutely nothing go on! However I agree with
@Morrus that we should support people who do speak out about industry bad behaviour.