When a rational and innocent person submits to a cop it is not because he has a gun, it is because the cop is doing his job, i.e. carrying out the 'will of the people' as codified by the law. Those who have a problem with that will quickly realize that they should blame the law and the system that created it, not some random guy trying to make a living.
But of course the rational and innocent people are not the problem. Sometimes you have to fight fire with fire, and that is why we have a police force. The problem with taking violent justice into your own hands is that the common person is not qualified to administer the law, just as your common person would make a pretty terrible math professor without proper education, training, and discipline.
Good point.