As a straight man, I am curious to see what other men look like, and I can certainly acknowledge when another man is attractive. But I just can't imagine having any kind of relationship other than friendship with another man. It's just not something that my mind is capable of, be it physical or emotional.

On a similar note, I would be very turned on by a MFM threesome, but only because I would enjoy the F with the other M. It's like watching a porn, only being there in person, and taking part in it.