The low pants thing reminds me of a prank video I saw online. Someone was walking down the street with the saggy pants/underwear showing thing going on, and someone in the car (filming this) squirted him in the butt with a squirt gun. The guy got mad and tried to chase down the car but tripped over his own pants. The car backed up & they squirted him a few more times while he was on the ground, and then took off again. All you could hear was the people in the car laughing.
I thought that was petty funny! It was kind of mean, but it was just water in a little squirt gun (not even a super soaker type, just a little finger-pump type - utterly harmless) so the only injury was to the guy's pride. And if the guy didn't have his pants down he'd have escaped their taunting!
I think it ought to be an accepted practice - if you see someone's underwear you should be allowed to squirt them in their rear ends. Since they're on display and everything!