I think it's their money, and calling it a duty makes giving feel like a tax instead of generosity. The other side might say wealth brings responsibility, and maybe that's fair, but I still feel people should decide for themselves. I'm not sure how to argue beyond that.

To me this comes down to whether generosity is chosen or forced. My opponent makes a fair point about responsibility, and I honestly don't have a strong comeback, but calling it a duty makes giving feel obligatory, and I just think people should decide for themselves.

The practical problem is that once giving becomes a duty, it stops being generosity and starts feeling like a forced bill, which people will resent or find ways around.