Actually BB, I assumed the same thing, but it looks like we're wrong regarding the ability type. Check out the Play As:
Baal Worship
Type: Evil Enh. • Brigade: Crimson • Ability: None • Class: None • Special Ability: Evil Characters may not repent this turn. • Play As: Prevent conversion of Evil Characters this turn. • Identifiers: OT, False Religious Practice • Verse: I Kings 16:31 • Availability: Prophets booster packs (Common)
So you still have to play it before any conversions.