The friendly fire kick is pretty generous at default, which is six. I don't tamper with it on the server I'm responsible for. It's called fire discipline.
Training Sergent: Well let's see... squad of twelve. You guys collectively killed sixty of your own countrymen today. Looks like you've met the bogie.
You! Stevens; You dropped eight. You're being court-marshaled.
I mean, really? Can you imagine a map where the initial tickets were 360, and the team collectively snuffs nearly 20% of the friendly compliment?
That's statistically worse than the Union defeat at Bull Run.
Snap out of it and play like most are capable of. In a real military organization one such kill might get you stuck at rank or retrained in a non-fire rating --if you were lucky. Two or more such incidents might get you a good long time in a labor camp.
Now in the game the artillery calls are a real hazardous role. Because as I've often seen, you can't seem to get folks to refrain from hurling themselves into it to save your soul. That might be the one place for code moderation, but I'm not sure it can be handled independently.
The server operators can set the bogie at a broad range, but keep in mind that even one vehicle kill will get you at the session ban threshold real quick.