I look at it this way: take any number of random people, and a certain percentage of those people will be assholes. For argument's sake, let's say 10% of the general population are assholes--a conservative estimate.
That would mean that 10% of soldiers who fight, 10% of our cops, 10% of our teachers...are complete assholes. And as it has been proven many times recently, some of those assholes get caught on tape.