The rule should be the same for all non-profits that wish to keep the tax exempt status.
If they want to preach politics they have freedom of speech, but they need to be willing to pay the taxes.
I think we should tax any church that practices discrimination as well, because ordinary non-profits are not allowed to discriminate. I know the "women shouldn't be priests" attitude is pretty entrenched in the Catholic Church. That's fine, they can keep that rule. But they should pay their taxes.