Yes, that is true as well.

My point was that since our cultural instinct is to give, but in practice this is done inefficiently, [charities are wasteful, people don't give to charities to optimize utility but rather to charities that they think they like, and a flat percentage is probably worse than a progressive tax], and therefore it would probably be better for society if we didn't expect charity from people - this seemingly beneficial cultural obligation can be argued to be harmful.