Too often is the word "militia" associated with radical groups or domestic terrorists. The legitimate groups police themselves, but have to bear the scrutiny of a cynical society, who just plain don't know what they stand for. All society sees are the law-breaking, radical 1% who make all the news in the main-stream media, and don't see the majority of the groups who train in case of emergencies where local/state/federal govts can't provide necessary services like security, disaster relief, etc.
Are there crazies out there? Yes, you will find crazies in all walks of life, in every corner of the earth. Some crazies operate differently than others.
Can everyone be policed? No, there are too many spread out over too wide of an area to weed out all the bad apples from the bushel.
$0.02, YMMV