Karate isn't everything. My dad knows something called z-attack, a stage after black-belt in which the tutor (whom he treated) taught him out of appreciation.
He told me that most martial arts will not teach you are to terminate your enemies properly (they are beginner material), but when you learn the z-attack, you know how to.
Even still, he did tell me that karate is not the solution to aggressive people as you can easily be assaulted. It is only there to boost confidence and perhaps a false sense of security, because it is not guaranteed immunity.
I'm not going to learn karate or anything like that, what's the point? You're giving yourself a weapon, rather than exercising your mental powers in dealing with situations. Wars are won by the powerful, not by the people with the most men.