I think that's an issue with all of them (and maybe just being that age in general), there's no grey, it's all or nothing, black and white. I think it's one of the reason's I appreciated Benny, for everything the others are going through, and even though Benny can be a douche, he also seems like the only actual grown up . Same thing for the homeless woman - them standing out there protesting, pissing everyone off is just creating a worse environment for them to live in.
Yeah, I can see this. I always thought the most telling line for Mark was where he says to Roger that he'll be the only one left (in the scene where they are fighting). The first time I heard that, it was like damn. His two closest friends, Benny being gone, (and at that age, probably the two people who matter the most to him ) are both HIV positive, which in the early 90's was essentially dying of AIDS, or at least that's how it felt. His ex-girlfriend is now in a relationship with a woman, and now enters two new people, bot who are HIV positive and one with an addiction. Yeah. I can get how he felt like give it another few years and he'll be alone.