Yes, men and women can just be friends.
But...the proper question is can "attractive men" and "attractive women" just be friends? That's much more interesting.
I have plenty of ugly female friends that I'd never even think of touching. With the cute ones, I can certainly just be friends with them too (and am with many), but if the opportunity presented itself and she was requesting the dick, I'd definitely have to think long and hard about my next move. I've declined some pretty hot friends before for the sake of the relationship...but it's definitely a case-by-case thing.
Pun intended?