I've heard that in that culture at that time it was pretty commonplace, but generally a man was expected to give that sort of thing up when he settled down and started a family. I guess they often returned to it when they got old... not my cup of tea, but to each his own, I say.
And even if Alexander was strictly a "man's man", so to speak, that wouldn't make him a sissy, necessarily. In the ancient world, there were elite fighting units who were... um... very, very close. They were also fearsome warriors (except for the downy-cheeked serving-boys...

).
If everybody in your platoon is "that way" it's probably very good for morale (as long as nobody gets too possessive

). And the sort of fetishistic masochistic elements of military life would definitely appeal to fellows of ...a certain nature.

Didn't they usually fight in the nude back then, except for a little armor? Sounds pretty gay to me... ;)

In the end (woops, no pun intended there), Alexander was never noted for his sexual exploits, more for his military exploits, so who cares?
Maybe Stone shouldn't have even mentioned it... although Hollywood can't seem to produce even a historical drama without lots of steamy, gossipy sex stuff...
