Whether Garithos and the Forsaken would've come to blows because he's biased against flesh-eating ghouls that're morally limited by virtue of their nature or because they're a transparent geopolitical threat to him is irrelevant to the fact that anything except gibbing Garithos would have resulted in her death and the deaths of her entire burgeoning faction. This on the basis of some kind of braindead loyalty to a deal that wasn't in good faith for either party anyway. Even a diminished Lordaeron reclamation movement in the Scarlet Crusade nearly destroyed the Forsaken let alone Garithos' much more coherent army that had foreign backing from Khaz Modan on top of it. Pretty much the only other choice that wouldn't have been retarded would be to have him possessed.