Why do some straight guys do this?

They hit on you and want to play thinking you're straight also, or are not bothered about you being biual. Yet if it was a gay guy they would freak out at that. One has been pestering me for fun but he was criticising gay guys and said he's disgusted at full gay. I mean, it's still another man so why does it make that much difference what the orientation is? It's still another male, and the bits are the same.