I am not talking about Robin-style trunks, just regular shorts that extend an inch or two below the crotch. Evidently men's thighs are so threatening that people recoil at the sight. That message board and many others have comments about how sickening and disgusting it is to see men's naked legs... honestly it's like Victorian England has returned.
You frequently hear the cliche, "Yeah, men can walk around with no shirt but women are not allowed to do this!" It's not true. Except for the beach itself or possible the fireworks, shirtless men get disapproving stares and mutters. And of course, no one can go without a shirt in stores, restaurants, theatres... I mean, seriously how many times a year do you actually see a man in a public place not covered up?
When you have been putting in those long boring hours at the gym (god!),eating carefully, and you look pretty good, naturally you want to show it off. It feels good to get admiring glances or even friendly compliments. This is why I totally understand why many attractive women enjoy showing off a little, and I don't find it a sign of moral collapse.. it's just human nature.