If I were to be a tax lawyer, I would be directly harming the ability of the US government to spend on social welfare programs.

Government social welfare spending is notoriously inefficient. So if your client is at all generous with his money you're coming out ahead. Heck even if he doesn't give to charity but does use the money to invest in productive enterprises, you're probably coming out ahead. And that's before taking into account how you spend your money.