What do you mean by "hearing your side" ?
If you did or said something that is against the TOS, then you broke the rules and you can get warned or punished for that.
It does not really matter if you got provoked or not, you are still held responsible for what you do or say.
As for how common your experience is, I can't say for sure since I am not a GM, nor have I ever been warned by a GM. Judging from second-hand reports here on the forums, I think the way you got treated is pretty much standard procedure when GMs get involved - they can see in the logs what was actually said so there is no need for them to hear anyones side.