When you summon your ghoul it should have a spell called Leap. This spell is like charge, but don't do any damage or stun the mob u do it on.
The spell text says ''Leap behind the target friend or enemy''. This means that you can use Leap on almost every target in WoW, NPCs and players.
I was in Shattrath once with my Death Knight, and i played around with Leap on other players. I wanted to try on a guard, which was neutral to me. And suddenly the guard started attacking my ghoul, killing it, and thereafter starting killing me. I tested this on different neutral NPCs in WoW. And all did the same. Sadly, you can't hit them back - Only if you put them ''At war'' in your reputation list.