I'm aggressive personally. Here, you can't pack with or without a license unless it's hunting or a firing range (and only with a license and outdoor's card - very strict rules here in Canada). I'd would have gone nose to nose with him too personally. No one intimidates me ever. Hubbs actually gets mad at me for things like this because I'm very much the rush right in and do my business type of gal. Especially when it comes to my children (blood is always thicker than water as the saying goes).
I've been a victim (child victim) once before, I'll never let another person make me one ever again. I, however, don't suggest being this aggressive if you don't have background knowledge (self defense for example, like I do) to defend yourself. It is dangerous and I really shouldn't do stuff like that but I get into this frame of mind about it and can't help myself at times. Thankfully, I haven't had to be aggressive like this since I was about 17 or 18 when two guys had a fist fight in the middle of a mall where we were witnesses. My mom must have shouted at me for forever afterward (knee jerk reaction to what I did) because I casually stepped between the two guys (and they both had a good 50 to 70 lbs on me) and separated them before security had a chance to get there.
I don't condone violence for violence but in some situations there is no choice but to defend yourself at any cost.
ETA: I'm verbally aggressive in situations where I see stupid stuff like you described. I'll go up one side and down the other verbally if I see stuff like that happen at a distance. It drives him nuts.