The reality is is that most TK's are an accidents. I doubt that anyone would intentionally TK; not because they care about you, but because they care about winning and getting the extra multiplier. So if you get TK'd, don't get pissed about it, because the other persons already pissed off that they did it.
In this very thread there's a player who basically says he has 10PS and he doesn't care if he teamwounds. What would make you think most are accidental? "I don't care at all about my team because my 10PS insta-kills means that my TKs will be negated and no one will know" is a more common trend than you know. These people don't understand what "team" means and think that their enjoyment of the game is much more important than that of others playing (who wants to sit around for 30 seconds because someone has a build "built for clusterfucks"), but as the system stands they are rewarded rather than punished.
Every time a discussion comes up about TK people come out of the woodwork to say "mostly accidental". Every discussion someone points out that they just don't care. Why is there this disconnect. The current state is that there is next to no penalty to TK so people TK as they please. Some people only accidentally TK, many simply TK cause they don't care about anyone else but their own playstyle and position on the scoreboard.
This type of play is most definitely rewarded. Swing left/right kill 3 of your team, but 5 of your enemies before you die? Well you now have a 2 / 1 KD and look pretty good on the boards.
A possible simple solution would simply to add a TK section to the scoreboard so that TKing a teammate isn't swept under the rug when you finish off the guy he had already wounded.