A quick question I had.

Recently, I raided the Warlocks tower and found myself face to face with the angel that guards the outer entrance. Being still young myself, taking the angel was a challenge. This challenge was added when several elder warlocks showed up and cast stoneskin and then sanctuary on the angel. I can understand the decrease in damage against the angel from stoneskin, but why would sanctuary make a difference when my character has a goodly soul? I didn't look at the angel's aura, but I would assume its either goodly as well, or neutral. I thought sanctuary was supposed to protect someone from attacks of the opposite alignment. I don't know. Anyway, I was using a wrathful weapon coupled with a mithril weapon. So, what gives?