It’s very easy for people to abuse the current system if they get mad, because there are no repercussions (to the player as an individual) for betrayals so long as any enemy has done any damage at all. Tracking team kills properly should mitigate this, with the bonus side effect of discouraging mindless spam and team nades.
The game should probably also track damage done to teammates and set a threshold before triggering the boot option. Again, it’s not hard for someone on your team who can see you through walls to just follow you around cracking your shields to completely shut you out of playing the game. And at a certain point it’s better to just play a 3v4 rather than have a teammate constantly feeding you to the enemy team.