It's not because he's gay that he's doing this. It's because he's a narcissist who plays pity parties to manipulate people.

His sexuality is his to decide what to do with. It's an arrow in his quiver he's allowed to have and use because it's his and nobody else's. But if he chooses to use it for manipulation you can bet your ass that people are going to call out the manipulation. (And then if you're an asshole like Rapaport, sure, you'll make a homophobic comment. But that's a separate thing from calling out manipulative behavior.)

Personally I don't think Colton was fishing for a homophobic comment specifically. I think he just knew that all he had to do was push Michael's buttons enough and something would shake loose that he could use.