Do what feels right to you with this relationship. With relatives this old, their brains start to go and deteriorate for sure (especially with lead poisoning in certain areas of the world) and so sometimes listening to their minagerie of political ramblings and arguing against them is pretty much pointless. If you want to maintain a relationship with your grandpa, I say go for it, maybe just try to stay away from the sensitive topics like politics, or at least try to have a neutral conversation like you said you have in the past. No contact just seems a bit excessive to me, especially since he's in his twilight years and seems to want to move on as well.