They are stealing from everyone. Churches do not pay taxes. This is supposed to be contingent on not engaging in politics and actually acting like a non-profit.
Some people might be able to claim coercion because tithing is required to participate in certain ceremonies, but I don't see how that's stealing (forced, against one's will).
«If the whistleblower’s claim is successful, that person could receive up to 30% of the proceeds collected by the IRS.»
Meh.