Of all the ways to raise "revenues", i.e. increase taxes, none is more insidious than limiting charitable deductions. Private charity exemplifies the humanity we feel toward our fellow man. No one forces anyone to give their hard earned money and time to complete strangers. Nothing is expected in return, only the hope that the needy are lifted from need, and that one day they can be givers as well.
Charitable deductions are a way for government to encourage giving, to encourage humanity. When government takes away those deductions, it by definition discourages giving and humanity. For liberals, government is the ultimate benefactor of mankind. It's telling and sad, that liberals want to take from charity so they can give to the needy.