The only time i could ever justify TKing is for revenge.
One notable Halo 3 match we had this annoying peice of sewer filth on our match who simply wouldn't shut up, he insulted everyone and figured that was a good reason to dictate gameplay, anyone who didn't do as he asked he yelled at, and it hurt our gameplay as it was so off-putting.
Eventually i snapped and told him I was going to bloody well kill him. I sought up out and tried to give him a few battle rifle shots in the face, although he kept dodging them, and then betrayed my himself. Next thing I knew the boot player option sprung up, so i was quick to shove that idiot off the match and got cheers from various players.
So I guess my point is that if your game has an option to kick player, and someone on your side is being an asshole, provoke them into killing you and kick the bastard.