How do I dominate Milligan?

In the quest "Necromantic" in Vampire: The Masquerade - Bloodlines, I read from IGN and GameFAQS(probably the same source) that I can make Milligan forget everything and earn a humanity point by not sending him to Pisha. Problem is, I can't figure out how to do it. I'm playing as a Tremere, I already tried putting a point on Dominate and using Brain Wipe on the guy but it doesn't work. No conversation options show for him forgetting everything too, plus there's no stat for Dominate.