Let's do one better than that. The RICO laws should be used against the ACLU.
I don't think RICO could be used against ACLU, at least not based on the stuff we're all familiar with. But they are clearly involved in both defending and prosecuting religious activities, and that ought to disqualify them from non-profit status.
They brag about how they don't receive any tax dollars, but the fact is that they get a tax subsidy from their non-profit status. And nine times out of ten, the government ends up paying their atttorney's fees in these lawsuits.