I have thought about this couple of time as well and I always conclude that it needs to stay.
Wheter you TK accidently or on purpose(and make it look like an accident), you need to be punished simply because it's not fair for the player you TKed to be the only one getting punished by your mistake.
The penalty makes people THINK a little before firing when they are crossing. It's better to punish the ones pulling the trigger.
Assuming SDE even knows how to remove TK penalty for mines, then yes, TK penealty needs to be removed for mines, but that's not what this suggestion thread is about.