I think some gay guys like the challenge of trying to get into a straight guys pants. Not to say that that is all they are looking for, but bagging a straight dick is an accomplishment, I guess. From the other side of the fence, think about how a straight woman feels when a straight guy hits on her, but she's not interested. If he continues on in his pursuit, he probably deserves to be shut down forcefully. I think the guy might think he's giving her a compliment by trying to get her, but she feels harassed. The same would be true in a gay guy-straight guy scenario. Yes, it could be considered a compliment, but unwanted attention is unwanted attention. You can call it flirting, or you can call it harassment. (And its likely much worse since society hasn't changed enough to support the person who feels weakest in the situation.)