I support the elimination of most deductions because they are just a means of social engineering and they cause market distortions.  But I hesitate to eliminate or limit charitable deductions because the charitable giving they incentivize is one of the better objectives that can be enacted by tax policy.

Sure, we can suggest and hope that charitable giving is such a high moral act that one  should not limit their giving by the tax deductibility, but I do not know that I would risk a reduction in charitable giving that may occur from limiting this deduction.  

This is a core difference between those who govern based on the way we ought to be and those who govern based on the way we are. It is the utopian verses the realistic.

If we are such noble creatures that the tax deduction will not impact our charitable giving then why did we initiate the deduction to begin with?  If this deduction will not impact charitable giving then why not eliminate all of the deduction?

If this will only apply to the very wealthy then where do you think the big donations come from? Do the wealthy not respond to tax policy and incentives?

In a more practical sense if we raise taxes on the wealthy they will have less money to contribute to charity.  If we raise taxes on higher income, capital gains, dividends, and also lower deductions there is simply less money to give, no matter how wealthy one may be.  

When charitable giving declines- and it certainly will- we can expect more class warfare rhetoric about how the selfish wealthy only give if the government gives them a deduction.  But the reality is that charitable giving will go down because the government will take the money instead.