Maybe I'm the only one, but it always irritates me when people do stuff like that. Those are the people who end up fitting the stereotype that is projected on us, and that hurts us instead of helping. It just gives the antis ammo to use against us, and it pushes the "undecideds" away from our cause.
What some people seem to forget (and some just don't care) is that as gun owners, we are constantly under suspicion and attack. It is important that we do NOT fit the stereotype, and instead project a better image as a community. Otherwise, its just an opportunity for the antis to promote their agenda.
My point is that people need to look at the bigger picture. While they may have a point they are trying to make by showing up brandishing weapons and wearing gas masks or whatever other crazy attire they decide to put on, it comes across very differently from the outside (and more specifically, from the other side).