Why were all the Germans assholes?*spoilers*
So they saved the pilot's life and then he stabbed him? Seemed like a dick move.
Then the kid gave him away when he could have just waited 30 seconds instead, and saved his own life.
It's not like every UK soldier was a saint, genius, martyr, or hero, either. The two heroes are great, sure, but there's Mackenzie who doesn't want to call off the attack, the lippy kid in the truck, the bitter guy obsessed with his flare gun - and so on.
Really, the kid yelling makes sense. He sees an enemy soldier shushing him, but this guy might be on his way to kill more people, stab the kid in the back, or even deliver a message that will stymie the German's ambush. While I'm glad Our Hero makes it through, I didn't think of the kid as a jerk. He was just doing his job, too.
On the other hand, yeah, the pilot was an absolute sphincter for stabbing somebody who just saved him from burning alive and was trying to get him water.