Is Bob a tax atty<quoted text>
1) tax rates vary with which bracket you are in
2) your tax bracket is based on "taxable income". This is income AFTER ALL DEDUCTIONS.
3) even if there were the magic "flat" tax rate of 25%, if you deduct right off the top, money you gave away, the tax you owe is less AFTER the deduction than before. Moreover, it would likely place you into a lower (less percent) bracket-- else you would not bother.
We all know you True Believers™ are as selfish as it's possible to be* so there is no incentive to give money unless you get financial benefit from it.
* proof? You believe the Ultimate Creator of Everything has a close personal relationship with .... you. That is the ULTIMATE in selfishness-- you actually believe the actual UNIVERSE was created just for little old you.
It just doesn't get any more selfish than that.
Evangelical Atheist ?