The way the scene is described, Harry has tunnel vision (which is not uncommon in combat situations) and probably tunnel thought. So, his thoughts were strictly focused on survival.
There's also the possibility that Harry didn't kill anyone. The RCV may have fed up in anticipation of the battle; or they may have killed the mortals in a desperate attempt to get the energy to flee and survive.
And there's the political angle. Either Harry is going to be handed over to the Red Court for violation of the Accords (in which case prosecution of him as a Lawbreaker is not only moot, but possibly a violation of the Accords) or the White Council is at war, in which case killing off your own membership is a bad idea.
There's also the key fact that Harry did not command or order anything. He gave the ghosts power, but not orders. He did not summon them, nor even speak to them except to send power to them. Yeah, it's a loophole; but it required the presence of a group who would attack. Had Bianca decided to have her soiree in a brand new hotel, without any ghosts, it wouldn't have worked.