I imagine the badge checkers are volunteers. Probably jealous they aren't playing! I would be! And really, I'm glad they're there. I had to pay my money for a badge, others should too.
I keep hearing about the bad attitudes, but never encountered it, even from those players who didn't have it displayed. Just a 'pardon me, let me see badges,' and a check of the GM's tickets, and they always moved on. Even when one guy complained, loudly, about having to get his out, the checker was still polite.