The staff are technically supposed to sort that out... not the patrons with their fists. There are things I believe are worth fighting for, are worth bleeding for - but this was not one of those instances.
Agreed, and it's one of my major pet peeves.
While waiting to be served at any type of service counter, I've always considered it a matter of courtesy to defer to customers in the order of their arrival.
I have, on many occasions, said "no, they were here first" when a clerk offers to take my order or offer service.
Nothing special, just common courtesy IMO.
I've also been known to turn around and take my business elsewhere when a brainless clerk doesn't take a moment to ask "who's next?" and allows some equally brainless a-hole to cut in front of me.
All that for assembly line, mystery meat tacos!