betrayed?

Why do I feel betrayed? Today my best friend tells me that Craig "slept" with my friend Eric. Now, I have known Eric for almost 8 years and he has always been one of the biggest homophobes I've known. And Craig is one of the most flamboyant gay guys I've known. Opposites attract? I don't know which one I feel betrayed by more. All I can think is that Eric went home with Craig from the bar drunk off his ass and crashed there. That there is nothing more to it than that. I really can't see Eric doing anything with Craig willingly. Which makes Craig sound bad. I know.
I guess it's stupid to even care, I don't want anything from either of them. I think I'm just being protective over Eric. Of course, it could just be a rumor. But Melissa said she heard it from both of them. Is it my place to ask one or both of them or should I just stay out of it and forget it? I really hate this.