Anger would certainly be a valid diet, and I suppose he could inspire folks to become pseudo-berserkers, but I dont think that feeding actually does much to reduce the emotion their feeding on. The Wraith meals dont seem to loose interest in sex or anything.
Yeah, the emotion isn't the energy, it's the channel the energy flows through.
After last night's posting, it did occur to me that Thomas was born on St. Valentine's Day, so if any vampire could learn to feed through Love, it might him. I'm not sure, though, that a Whampire that successfully did that would still be a Whampire. Thomas might then have become something else, maybe something unprecedented.