Donations to certain charities can be tax deductions, but once you give the money to the charity, it has to be used for charitable purposes or it's not tax avoidance, it's tax fraud. Having it be used for charitable purposes seems like the thing we should want to happen to it.

Moreover, most of the things traditionally thought of as tax avoidance don't involve charities at all and are more along the lines of warehousing wealth in offshore companies where it can collect interest at low/zero tax rates.