That changes nothing about how "voluntary" that "voluntary commitment" is, that you can, at your own will, choose instead of paying the same amount in taxes. I

That changes nothing about how "voluntary" that "voluntary commitment" is, that you can, at your own will, choose instead of paying the same amount in taxes. If I point a gun at you and ask for your wallet, you can voluntarily give it to me, but that doesn't make it less of a robbery.