Why do people think its weird when a straight guy has a gay or bisexual guy friend?

Okay so i have two friends of mine They are both bisexual ( open very openly other not so much). I don't understand why people think its weird when they find out i have a gay or bisexual male best friend just because im straight. I mean im straight and i dont mind being friends with them ( they realy help when i want some nice clothes) as long as they dont try to have sex with me. (which they would never do an i trust them). I dont like random gay guys hitting on me when they know im straight so automaticly people think im homophobic its not that i just dont like them trying to be all obnoxious an say oh i could turn you. ( thats when my friends come in an defend me ). I thought it was just straight people that thought it was weird but some gay guys think its weird to, like just because im straight im instantly homophobic an by supporting gay rights i only support bisexual girls. i explained to him that i understand he is gay an was born that way an cant control it. But he also has to understand i am straight an was born that way an i cant control it. So why do people even gay men think its weird when they find out some of my best friends are bi/gay an they are guys