I see no problem with a pair of basketball shorts or sweatpants in the heat of summer, but some people wear this outfit throughout the entire year.
Shorts are never acceptable for men outside of sports or beach wear. And when it comes to wearing shorts for sports, they have to be above knee-length. Björn Borg, Bob Cousy, and Franz Beckenbauer were not afraid to show their legs, why should men today?
(Steve Bannon, of course, is exempt from this rule)
My, what awful judgmental people we have here. I wear basketball shorts and more often than not polyester 'jersey' type shirts (but blank) the entire year because even in cold weather I get hot quite easily, especially if the sun is out (and I'm allergic to denim on top of it.)
Unless you're not in some formal occasion there's no reason to dress in any way other than what you feel comfortable in, as long as you're not being lewd in the process.