Offering plate money is not exempt because of IRS law. It is untouchable because of the first amendment.
There is a legal case that can be made for ‘deductions’, but there isn’t a constitutional case that can be made for donations to God. That belongs to God. Therefore, it is entirely outside the realm of government.
If an oriental Buddhist leave a basket of food before an idol of Buddha, does the government get 2 of the bananas and 3 of the apples?
What is this first amendment you speak of? Language and law are now merely tools in the hands of the oppressor. The courts are corrupted and can craft language to legitimize any offense committed by the dictatorship of the US government.