My sense is that the government should not try to tell me where to give. Indeed, I am a churchgoer. I give to my church. When I went to Australia, where there are no tax credits, I still gave the same amount to my church. Frankly, I haven't come back to actually sending the government back my money that I get as a tax credit. But I don't need that.
My sense is this: is that really a prudent use of government resources to encourage giving that would take place no matter what, whereas to tip the balance in some areas, so that giving is actually more responsive in areas that perhaps are a greater need, that would be important?
In Australia, as in Canada, a large minority of private contributions already go to religious organizations regardless of whether or not there is a tax credit. In Canada, it's something like 46%. In Australia, it's something like 39%.