Not quite sure I agree entirely with the title of this video, in that these prank comedians are getting what they deserve. Getting punched in the face is pretty harsh treatment.
Still, some people will no doubt feel that if you go to a large city and mess with the wrong person, inevitably you're going to rub them up the wrong way and they're going to react.
It just so happens the reactions here tend to be eruptions of violence, mainly consisting of a smack to the face.
They should just be glad that's all it is. It could be far worse.