tl;dr: have a friend who has historically always been mad when his friends got a gf/wife. He acts like he's 15 years old and saying "bros before hoes" still. He calls me and other friends a yuppie or breeder, and he thinks crosswalks are authoritarian so he has to always be a "rebel" and make it seem like he has the most unique viewpoint in the world. He doesn't change anything about himself, and he's stubbornly proud of having "no filter." This has caused every wife/gf of his friends to not like him. He will never be invited to any kind of social event because he will say stupid shit. Like, nobody has to be a rabid commie all the fucking time. Him and my gf got into a huge fight because he always talks like an asshole, and i live with my gf, so he doesnt come to my house at all because he'll say some shit. He still brings up this fight when im around him, and it's like get the fuck over it. I basically don't share anything about my life that involves my partner now, because he'll say something fucking stupid about her. He also begins a lot of sentences with "well" or "actually" which is never helpful. He literally can't admin when he is wrong, even about the simplest shit.
This really all seemed to get worse once I started my current long term relationship, and then it got way worse when my gf got sick of his shitty attitude and how he treats everyone like an asshole. He literally just can't be chill at all. No leftist(or similar) should be ranting constantly about every single injustice during every single social situation. That is exhausting to be around, and there is a time and place for it, but there has to be an ability to switch that shit off.
Finding and keeping relationships requires changing yourself just a bit, and making compromises, and it's now become apparent he isn't capable of that.
related question: have you ever dumped a long time friend? This is all a somewhat recent change, like the past 3-4 years, and it really seems to be because im in a relationship like most of our friend group, so now he's totally alone. Ive heard him say he's in therapy but i have to wonder if that's true, because it clearly isn't working. I'm annoyed by him but I pity him too because he can't fucking change for anybody at all.
It sounds like you've done all you can.
It's not your job to fix your friend - that's his job.
A friendship is not a deposition - you don't have to tell him everything.
It sounds like you've brought up all these issues with him previously to no avail - it's totally fine to just distance yourself now.
If he realizes you're less available and confronts you, you can tell him that spending time with him is stressful for the reasons you've previously brought up, and you haven't been up to dealing with the additional stress. This leaves an opening for him to at least attempt to behave more like a friend engaging in mutual care than a personified rant, and gives you an out for ending visits when he does not.