My Grandfather Hasn't Spoken to my mother in 35 years?

...because she married my father (whom he didn't approve of) Then he divorced my grandmother for his secretary and had his attorneys put her out on the street. He and the secretary moved in to her house and she lived with us ever since. That was 1978. He's a widower now, late eighties, and mean. I heard he had nobody (except for two step kids out of state) so I've been going to visit him. He's not very warm to me at all. Sort of treats me like a bastard. And my mother he's disowned. I'm only seeing him because I know he's so alone, living in a home. I'd do it if he weren't my grandfather. However last night, I phoned him and an otherwise light conversation turned nasty when I suggested he "forgive" my mother (for what? she did nothing) and speak to her again. I made the point that "If god had a say in this, he'd say you should at least let her know you love her. She only doesn't come to see you because she's afraid you'll reject her again" He said "don't hold your breath buddy" and hung up on me. It hurt very bad. I've done nothing except try to reach out to him. I was searching the internet for "unsafe people" --- I've heard my mom use it regards to him. A pop psychology term. Why do I feel guilty? Just for bringing up that he should reach out to my mom? I feel like I'm trying to save him from himself or something. Save his soul. And I feel ridiculous for it. I've seen my mom cry about her father not loving her for 30 years. I knew him when I was a boy and he seemed to love me then. I guess I'm looking for that grandfather, but he's not there anymore. Just someone full of bitterness and condemnation. He hated my father (dad was a junkie. And he sees me as the spawn of a hideous error on his daughter's part) I'm a grown person now and successful artist. It's like self abuse to relate to someone who makes me feel like this. But it feels wrong to let him rot. Is this the point I just let him die?