But you can't have 2 sets of rules. One for big and one for little.
What they need to do is examine each churches income and evaluate how much is used for legit non-profit stuff, like food banks, soup kitchens, shelters, legal aid, etc. If the income beyond that is over a certain % of what would be required for normal maintenance and upkeep of the day to day operations, the rest should be taxed heavily.
Beyond that, not only is it highly unethical (religion is never unethical though *snicker*) to tell people that their standing with god depends on the amount of money they give, but it's damn near fraud.
And I'm a well documented atheist around here, but it all reminds me of a pic I saw once on some other forum:
A simple concept but so many Christians forget that, and think it's all about how much money you give, what party you vote for, your beliefs on birth control, guns, patriotism, etc.