As for public servers, I only play on them and most games are great ones, maybe 1/3 of them has one or more TK´s.
If I see someone teamkilling and its obviously intentional, I kill him and/or start denouncing him and asking everyone on the server to kill him on sight. Yes, I prefer an escalation strategy. Youre right, TNT, most of them TK´s are just bored, but do you think to be bored is a stringent reason to TK? No, we´re all bored, too, sometimes and I dont kill team mates on purpose. A TK isnt just bored, he lacks of something we all call RESPECT. And the only way to learn to respect the other gamers on a server is being beaten to a pulp by the other players until he´s not bored anymore but really annoyed and leave or adapt.
Last game with TK´s I remember was on Omaha with 2 or 3 real TK´s on the allied team. The TKing escalated to a total DM on the allied ship during one complete game, there wasnt one single boat reaching the beach. In the folliwing game then all of a sudden all TKers were gone, not one remaining. I dont think they will TK a lot the next days
. The good thing is nearly all TKers really suck, total lack of skill, and if you make them painfully feel it they will consider twice about TKing in future.