My father was in the Vietnam War. He was also a drill sergeant for years after he recovered from injuries.
My understanding is that such things were quite common. And retaliation would normally end with the private getting their butt kicked,by the sergeant.
The sergeant, in many cases, tries to create a situation where the troops bond over their distaste of their drill sergeant. An army is a chain. Only as strong as it’s weakest link. In this case, the sergeant knew that Pile was the weak link. He put it on the rest of the troops to pull him through training. Just as if helping a wounded soldier, in a real scenario. They must work in unison, and take up each other’s slack.
Behavior such as seen in FMJ, was eventually frowned upon. Sweeping changes were made. Now, they aren’t supposed to touch the troops, and can be reported and/or punished…
In the time that FMJ was taking place, Pile had no choice but to pull through. If it were earlier in the war, he would have been sent to jungle training, after basic training. So, he lucked out there. But, as we know, (spoiler alert) Pile spiraled down the steps of insanity…