Here is the covenant between zombie lovers and keepers of order.
We understand that for whatever reason, you have the compulsion to aid the enemy. Fortunately this is Azeroth and not America, so you won't be sent to Gitmo as a result. We don't really care what your motivations might be (though most assessments are less than charitable).
You must understand that there are those among us that will remain true to our chosen affiliation, and part of that is the maintenance of order around our auction houses, banks, and so forth. As followers of the light, it is entirely correct and consistent for priests and other healer-types to try to protect what is ours.
It is a game, a completion between two different mindsets. As long as you accept it for that, I have no problem with what you are doing, and I'll be fighting the good fight and putting down zombies wherever I see them. It's consistent in my idiom, the same as inconveniencing your own faction is consistent in yours.
However, if you insist on harassing and insulting people that thwart your plans, the line has been crossed. Here on out, you will be reported. Blizzard created this problem ((What were they thinking? They must be pretty out of touch not to realize this would happen.)) , they can damned well deal with it.
Play nice, and I will, too. That's the deal.