1. Because it's unconstitutional.
2. Because religious organizations are not accountable to the citizens who subsidize them.
3. Because it's easily and routinely abused.
4. Because it costs you and me Billions.
5. Because the founders got it right.
6. Because it's fundamentally unjust.
7. Because our country is not supposed to be a theocracy.
8. Because it makes no sense.
Go to http://taxthechurches.org/ if you want a more detailed look on what these mean.
Many amass great wealth and vast media empires - all of it off the tax rolls. The point is that religious organizations can and do espouse doctrines of intolerance and hatred, filter funds to foreign enemies, and cause far more harm than good in the community .