Soo i was on with my shammy on a private server (arcemu), i went in dalaran and i was spamming chain heal with target on me and i have seen i was healing the Horde too (im alliance) after this i put on my searing totem, and keep chain healing, and from nothing my searing totem started to attack horde, after few secconds horde appear to me as Hated, so i was able to attack them but them no,
//Update
i used unstuck and unstuck tele me to starting race location but the bug was on soo i still was attacking horde but they couldnt, that in all locations, anyway im posting it because it may help you.