You can not support someone or something and prompt others to do the same as an intentional effort to hurt that someone or something. You can also not support someone or something because you simply don't like that someone or something. I've seen plenty of people refer to the first example as cancelling, and it is. I've never seen anyone refer to the second example as cancelling. If you have, post an example.
Not everyone changes the way they speak as they grow older. That's not at all unusual. If you think Dave should and don't like the fact that he hasn't, that's fine, but I'm not sure why you feel that a lot of other people have to share your same hangup. To be honest, I also find it kinda cringey, but a lot of fans of comedy and music don't really care.
I don't really think he's complaining about how it used to be. I think he's catching feelings because some people aren't taking his material the way he wants them to take it, and he seems incapable of accepting that and moving on. I agree 100% with the sophmoric humor. If anything, I think that's what would hurt his legacy.