I find this man often, with PvP toggled off inside the Horde capital.

For those wondering how he does this, I will explain. As an Alliance player, I have done this quite a few times. Everyone pretty much already knows you can fly into the capitals and get pretty far without being dismounted sometimes. 

If you aim high for the right side, you can land in the hallway which leads to their portal room without being attacked by guards. I've always been flagged as soon as I enter, but I play on a RP server where world pvp isn't that big. 

If you can make it to the portal room and no one bothers you, just wait 5 minutes and you're unflagged! ;)