I don't believe it would infringe on freedom of religion. It might be a game-changer, though, as religion might claim a right to use public property for religious purposes, since they would be taxpayers and have the same rights as any other taxpayer.
I'm not sure what you mean, or what you think would happen. It's not like corporations are running around taking public property for themselves... and to the extent that this does happen, churches already play that game anyhow.
The wealthier churches which would pay more in taxes would probably feel entitled to greater consideration than the impoverished churches which would pay very little in tax.
Again, I'm not sure how this is different from what happens now. I've witnessed firsthand churches trying to throw their weight around based on their size ("our congregation is X,000 people and X% of them live in your ward, Mr. Councillor"... with the implication that if the councillor doesn't go along with what the church wants, they'll see to it that he doesn't get re-elected).
Yes, I agree, although I also agree that there is a social benefit in keeping non-profits exempt from taxes. The fact that donating to them is tax deductible is a great incentive for people to contribute to private charities. Without that, then I would expect many charities to go belly-up, which would then require more taxes be used for social services to fill the void.
So, yeah, I guess we can tax them, but then it would just mean that the government would have to pay more for the services that would go away if private charities were diminished.
But what services? I don't know the exact wording in US law, but in Canada, "advancement of religion" is a charitable purpose in and of itself. IOW, a church can function as nothing more than a god-based social club, providing benefit only to its members, and get much better tax status than a similar social club based around, say, cultural background.
I guess what I'm trying to say is that we don't have a clear picture of how much actually charitable activities churches do.
In any case, my preferred approach wouldn't be to start taxing churches across the board; it would be to simply remove "advancement of religion" from the list of charitable purposes and treat each church accordingly. A religious charity dedicated to poverty reduction wouldn't lose its status, but a church that provides benefit mainly to its members but makes no profit might see its status downgraded.
(note: in Canada, charitable status and not-for-profit status are different. To qualify as a charity, an organization needs to be primarily devoted to charitable acts or "advancement of religion." If an organization doesn't qualify as a charity but still doesn't make profit or have share capital, it can qualify as a not-for-profit. For instance, my car club is a not-for-profit but not a charity. Neither category pays corporate income tax, but only donations to a charity are tax-deductible.)