There's a server setting for this, just turn off the friendly fire autokick. That's all the forgive system is used for, anyway.
Automatically forgiving the killer is undermining the purpose of the system. Most TKs result from poor situational awareness or poor fire discipline, and that needs to be penalized at some level that is relevant to the player. A tiny score penalty is not relevant, but getting an enforced time-out is. The default threshold is fairly large, so if you're racking up so much friendly fire that you're getting autokicked, then a poke from the game to tell you that you really need to work on that is entirely warranted.
Personally, I don't care if someone is "sorry". Being sorry doesn't make a blatantly stupid TK any less stupid, and it deserves to be chalked up as an error. If I've gotten myself TKed through my own risky actions, like charging out of smoke from the enemy side towards friendly positions, then they shouldn't be sorry anyway, because they didn't do anything wrong; it was my fault, and I can own up to that without needing an unwarranted apology from them.