Of course there can be bars in establishments that are not necessarily bars.
But in a stadium where you've got people selling burgers, dogs, cola and beers from behind a counter, I wouldn't call that a bar!
As for the barman/barmaid debate, we've got a wonderful gender-neutral term: bartender!
I'm with you on this one, at a stadium food stand it is not a bar. If you look at a diner that sells beer and wine you would not call it a bar.