Should I be? :spotted owl:
The diabolical capacity is present, the questions is "would I?"
See, the problem with this isn't people team killing. It's retards intentionally running into your line of fire so you accidentally hit them, losing XP. I've seen it done many time in the old ages of TK banning. If someone didn't like you, they run on top of your grenade, die, and boot you. SSDD. If they don't like you, they'll run into your bullets, lose some health, you lose valuable XP, they don't lose one... These types don't care if they die, they're having fun annoying you. The only way around that is either very careful shooting or disabling FF.
For that reason, I never put FF on, if I have a choice.