Reading this forum, I can see that the women generally see nudity as an art. The men see it as sex.
For this reason, women accept both female and male nudity. And for this same reason, men just can't accept male nudity. They can't look at a naked guy and disassociate the image from the notion of sex. If they even remotely indicate some acceptance, it's like they are opening themselves to the possibility that they are homosexual. Imagine what their beer-buddies would say!
A guy just cannot like another guy's body. And no guy has ever appreciated Arnold Schwartzeneger's muscles with some small amount of envy!
Look at the guy on this forum with the picture of a man with muscles... isn't he appreciating that man's body?