I've been thinking about this whole town-hall thing more than I probably should be and I've come up with a couple of thoughts:
a. It's illegal to yell "Fire!" in a theatre or "Bomb!" on an airplane because it runs a pretty high risk of inciting chaos. However it's become apparent that bringing a loaded assault rifle to an already tense political event is perfectly acceptable. These people may have the right to do bring guns wherever they want, but if precedent from the 1st amendment applies they really shouldn't.
b. We are seeing the comfort zone of relatively extremist individuals being expanded. Right now they feel pretty vindicated and/or proud to be bringing guns to rallies, but what happens when that becomes so commonplace that there is no longer much thrill in it? Where is the line going to be drawn here? If you let people get away with stuff like this over and over eventually they are going to push the limits... what that entails is anybodies guess at this point.