Don’t exploit bugs in the terrain to stop them from being able to retaliate. Don’t collaborate with the opposing faction to gain an advantage over other players (since you mention an Alliance main, that one sounds like a real possibility).
As long as it’s just you and other Horde players roaming Silithus and slaughtering any Alliance you see (and not, e.g., logging onto your Alliance character to find out who’s where so your Horde characters can track them down more easily), you should be fine.
At the moment, there is no clear indication that this is a violation. It’s highly suggested to not take part in this since it could result in your own reputation on that realm to be kind of blacklisted from being invited to groups to do certain things. That is more controlled by the the fans though.