It usually doesn't happen quite like that. But sometimes it does.
I avoid being kicked by: playing with friends, using team safe gold, eluding jerks if I do get teamed with them. Sounds like you were probably playing arena. When I play arena, I stay far enough away so this kind of thing doesn't happen, and no one steals my kills. But I also stay close enough as to where I can quickly revive my teammates.
I HATE kill stealing. And randoms are typically the worst. And I try to be super careful not to do it myself. I play co-op a bit reserved (unless I'm on a speed run type treasure hunt w a friend) and therefore may have a few less kills than some others, but I'll also often be the guy w 0 deaths at the end too.
On co-op and team modes, I always hear people complaining about these. I mean, jeez. I've gotten many kills stolen from me, but I don't care because it's still a point for me. Not in terms of cash, but in terms of co-op scenario progress, or number of kills to win a game.
Although if you count kill-stealing as people you shouldn't play with, I have tons of those. Hell, I do it myself, all the time, and I *know* I stole the kill because I can see my mates trying to kill this guy.
Wanna know a neat trick for pissing off people and not getting kicked? Use paid bargain bargain and thanks buddy with Cursed Idol. Everytime you TK a teammate while cursed, you wont get you kicked AND you can do it as much as you like/can. Works wonderfully in TDM where all the tryhards and stat padders are.