Players are already punished heavily with huge minus points in PR. So now they get banned for that.
What if it were a mistake? I mean look at Afghanistan and Iraq, a blue-on-blue incident happens and was deliberate during the event. When they fire the shot, they are as sure as hell that it was the enemy they were shooting at, only to realize it was a mistake later.
Participating in a realistic combat is including mistaken TK (excluding equipment whores), which is already punished by points in PR, and I think that's enough.