Because you can never know when one will decide to knock you down from behind and trigger a spontaneous mass stomping party like that.

There is a reason why "bait cars/bikes" used to be such a popular method of policing. Because niggers are always just the opportunity away from committing to a crime, instead of a need.

So all it takes is one slightly braver negro to throw the first punch, and suddenly all around him are jumping in for the chance to chimp out despite there being almost no possible gain from it beyond "well it was there."