I get that it's a cultural difference, but the grandfather really did seems like a scumbag, who belittled and abused his son because; either he disliked that he was the spawn of his original wife, disliked that he was closer to his original wife than him, or disliked that he married someone who he disapproved of (and who is he to give such advice given the previous point?).
The father has every right to not visit him on his death bed and loath the dude, it's filial piety taken too far otherwise.