Don't let them intimidate you but do not give them the look. When you give them the look you have given them exactly what they want. A response. And yes get the dash cam. It may keep you from going to jail one day. That is unless you give them the look, or give them the word, or the finger, or flash them a look at your gun. Then "you're" the one in trouble.

I'm sorry you are having to deal with these people.