I wouldn't put up a stink about someone holding a space in line for their buddy, but if someone just walked up and placed themselves in line amongst a bunch of strangers, that's a different story. You are a dick head.
One of the rudest things I see at gunshows, and it's happened to me many times is this: I'll be standing at a vendor's table looking at their stuff. Some f*ckstick will actually squeeze right in front of me like I'm not even there so he can look. WTF?! #1, you're being a selfish inconsiderate jerk. And #2 you actually had to brush your ass against my crotch to squeeze in front of me and then bend over to get a close look at whatever you think you're going to swipe out from under me. Seriously guy?!! I'm no homophobe but that makes me pretty uncomfortable. So much so that I won't even say anything to the dude because it's such an awkward situation. I hate you for that, you weirdo butt-shuffling ghoul!!! Go to hell!!!!