How come so many of the gay guys who bitch about how effeminate gay men are tend to be effeminate themselves?

A lot of gay cis men aren't really aware of how feminine they are.

I rarely see butch gay men bitch about how femme gay men

I see that a lot, but it's usually for the same reason. It's due to fear of their own internal femininity, and that it makes them look extra gay. Guess what boys? It does make you look extra gay, how about that?

I once went to a "masc" event which my ex invited me to (or else I'd never set foot on it because I'm a queen) and these dudes were so forced in trying to emulate what they perceived to be masculine. I sat next to a guy who kept grunting for the entire meal. I mean, you know the guy probably listens to Madonna.

LOL. Masc is a fetish for some guys, and it's mostly about appearance, not mannerisms (although that's a factor for some guys too).

Also that guy who was grunting...maybe he really is like that. There are some dudes who really are Neanderthalishly masculine, and they who really don't seem to be compensating for anything. It depends on the individual.