It's one thing to suspecd belief for a "murdurous rapeing villian", it's another for a dude that acts like my fraternity brothers. It's a little closer to home and therefore, a little more personal. One can identify with said character. Not many folks can identify with a "murdurous rapeing villian".
I'm not saying he doesn't do a good job acting the part. He does. Just in the back of my mind..
Think of it this way. Most gay men spend a heck of a lot of their lives pretending to be straight, so it's not like they have to put a whole lot of effort into acting as a straight man on TV.
The only movie I've seen with straight actors playing straight men convincingly was "Priscilla Queen of the Desert"
Brokeback Mountain didn't even come close.