Why do gay men not respect people's relationships?

Even though I am gay, I don't ociate much with the gay scene. I have a boyfriend I've been with for two years, but beyond that, I have no friends and don't go to gay bars, clubs, etc. Everyone I know is straight. My BF has a few gay friends he hangs out with, however, and they lead very promiscuous lives with all these people. Half of them are just friends, yet they sleep with each other for fun. And they don't respect anyone's relationship. They don't care if you have a BF or not. Two of these guys hit on my BF, and I made it clear I was not okay with that. And upon tagging along to a gay club with them once, I discovered it seems to be a general attitude that just because someone is in a relationship does not mean they're off limits. It saddens me that most gay men I know have not the dignity to respect someone's relationship...and it's exactly why I stay out of that scene. Because of this, I don't even like my BF having gay friends, because none of them respect the fact you're with someone. Does anyone else have this problem, and is this just the way the gay world functions? Is this just the way it is?