I disagree. Team damage adds an aspect to the game that makes it feel a little more realistic instead of just "Mariocarts with Guns". While there are certainly jerks that abuse the system, those jerks are usually not seen that often....at least not in my experience. Those jerks will still likely be jerks, even if team damage is turn off.
Myself, I like the intensity that team damage provides. Situation where I could shoot at the red tank, but I might hit the green tank. These situations cause me to actually think and consider the consequences before I pull the trigger. It causes me to work with other HTs at the choke point so that I do not pull in front of their shot....or so they do not pull in front of my shot. i also like to place my tank where a red tank might kill the other red tank when I am in a 2 vs 1 situation. There is nothing as satisfying when you win a 2 vs 1 because one red tank killed the other.