Mutombo shouldn't go to the stands, nor should any player, but at the same time, they have a right not to take that type of abuse. No one does, public or private, doesn't matter. Just because one is a celebrity doesn't mean you can go off calling him/her racial slurs, that's just ridiculous. It happens, no doubt, but doesn't make it any more right. If anything, players should be given the right to remove fans if they're heckling them too much.
It's one thing to say "you suck" or "fat ass," but to insult someone's creed, skin color, or family member, is intolerable. Those qualities are what defines humans, not a player. Being overpaid or lazy defines them as a player, but when you start getting to who they are first, which are humans, then you cross the threshold and deserve to be punshied.
That's my opinion. In high school games, I heard racist slurs from the stands like "****** don't play basketball," , "your mother sell good fried rice" and I would've love to run into the stands with the bench chair, or throwing my own racial jokes back, but I guess people are always idiots.