Justin Bieber Says Floyd Mayweather's Critics Are 'Stupid'

Justin Bieber and Floyd Mayweather have been buddies for a few years now, doing the kinds of things 21-year-old pop stars and 38-year-old undefeated champs tend to do when they’re in the same room: launch apps, box shirtless, wear sunglasses indoors. You know, totally normal stuff like that.

So it should…