He announced his disease and hoped to continue for a while. It was known at the time the movie was made that he was an alzheimer's patient.
Damo, so he announced that he had the disease and then continued in his position as President of the NRA. Now, i can understand their position being one of, listen, anyone we get to go around screaming "Out Of My cold Dead Hands" after a bunch of kids have been shot up is bound to be a half-wit of one sort or the other, we might as well stick with the half-wit we know. It still remains that he was in that position, that the NRA kept him in that position, and that when you head up what some people (myself among them) consider to be an outright EVIL organization, and you sit around crying about it's not fair because I was a half-witted evil bastard at the time, don't expect much sympathy!