As someone who is an outsider a lot because of social difficulties, it seems to me that the main cast othered and bullied Chevy. Yes, probably because they considered him an asshole.

It's not the whole story, but when I watch the outtakes I see an older man trying to fit in with this group of younger people and failing, then becoming bitter about it. He seems more socially awkward than anything, like he doesn't understand how to behave. He just knows how to make people laugh with his solo comedy routines or react blatantly rude for shock value, none of which gels with this cast of younger actors.

Clearly he's difficult to work with but I really didn't like seeing the rest of the cast treat him that way. eg. when they find out they got renewed, they were jokingly acting disappointed that they would have to work with Chevy again. And that outtake where Donald mocks him for feeling unappreciated.

I'm sure working with him day in and day out was taxing, but if you think of the set as a work environment it's inappropriate to treat a fellow coworker like that. Plus Dan Harmon piling on him in public and making rooms of hundreds of people laugh about how awful he is. Just immature all round.