I usually try not to push people on this particular point unless I think they're already very high-level; my default assumption is that people are very akrasic and fragile when it comes to charity.

However, I'm raising my estimate of Landsburg's level based on this - I guess one mostly hears about the disputable points he got wrong, not the indisputable points he got right, of which this is one (and a rarely appreciated one at that).