I know you don't like her like that, but I can totally understand why her boyfriend got pissed. Would you want your girlfriend hanging around another guy, that she had a great connection with all the time? When she is dating other guys, respect their boundries, if they aren't too unreasonable. It doesn't matter if you think they are douchy, or not.
My ex-girlfriend had another guy hanging around all the time, and it irritated the crap out of me, because he was constantly interfering, but the thing was, he actually tried to ask her out a long time ago, so he did have feelings for her, at least at some point.