Eactly. So it's not possible to get charitable out of it because he is greedy already. 50% chance to add charitable... but he IS greedy at the moment of the decision. And the 40% option to lose greedy does not include giving him charitable. The 50% option needs to remove greedy and add charitable.
If you have the trait greedy and get another event which will give you charitable, greedy will disappear and you'll get charitable instead.