You should. That kind of behavior is outside the scope/rules of the game unless both players have agreed to it. So unless you and the other player have agreed to it before it happens, then the other player has broken the rules. At the very least, he needs to be made aware of the rules before he tries doing it to someone else who doesn't agree to it.
That's not what the Titans (I think) said when I complained about it happening to me.
