Don't be vindictive because you hate a position

So today I was taking orders on the top speaker in drive thru, with another person in the back taking orders on the other speaker and taking money. Literally every other order that they took was incorrect in some way.. whether it was that the order was missing something or the person was rung up for the wrong size or the wrong drink, there would be chaos for the presenter as people would complain about their wrong order.

The person in the back was complaining about being in the back, and loudly so. They had enough sense to not do it in front of the customers, but everyone else could hear the person complain. I'm pretty sure that it was even somewhat intentional that orders were being messed up-- after all, mess up enough and that encourages managers to remove the person from the area for the sake of keeping the line moving.

I see this as good and bad. Good because you need the best possible person in a spot like that. Yet bad because it feels like it rewards people for being intentionally crappy and puts more work on other people. People who whine typically get thei way while people like me who do their job end up wanting to go crazy.