While I agree that this was a humorous and fairly positive event aside from wasted tax money, I have two things to comment.
First, pretend or not, I wouldn't want to crash an anti gunner party or any other party any more than I'd want an MOC meeting to be ruined by brady bunch types. I would consider it bad form, regardless of the type of sub human scum I might miss out on the chance to piss off. Second, I don't think I'd ever prank anyone like this. Me and some other men and women walked in and around the Capitol building of Michigan with long guns and side arms, even posing for pictures on the capitol steps and in front of the governers office. This was pre planned as part of the Second Amendment March, and almost welcomed by the capitol folks. But on the other hand, we decided against crashing the party for an anti gun rally set up by Jesse Jackson.
Being an outsider from a categorically different place, I'm not trying to insult or judge the way this was done, instead I'm attempting to provide outsider perspective from a closer to free state with lots of successful activists, just as food for thought.