Way beyond Frenchman rude.
One of them had a little smirk, as if daring the flight attendant to try to do something about it. I think she should have made him move, but on the other hand, we probably would have had to turn back if he had refused and the schedule was already out of whack because of the snowstorm. Something of which he was perfectly aware, I’m sure.
Or maybe they figured the two rudeniks wold be better off together than one next to some other hapless passenger who was going to take that seat.