"A man wearing shorts above the knee is seen as repulsive or even threatening."
Yeah, I've had to give in and switch to loose jeans for that very reason. It's a stupid attitude -- we're in FLORIDA, for Christ's sake!!! It's humid as hell and over 90 degrees for 8 months out of the year! The natives down here didn't wear loincloths just for the hell of it! -- but I got tired of people giving me disgusted looks whenever I sat down. (My gym shorts hit knee-length standing up, but they'd ride up whenever I sat down in class.)
Anything heavier than a pair of gym shorts is as hot as jeans, so you might as well go all the way.
Besides, at least you can wear boxer shorts in a pair of jeans -- the material's sufficiently...restrictive to prevent embarrassing moments.