Blizzard, I’m sure most of us have family members who don’t agree with us on important issues like you describe. I, too, have had unproductive exchanges like the one above.
In my opinion, your relationship with your grandfather is more important than whether you get him to agree with you. Assuming you feel the same, direct confrontation is probably not the way to go here. Maybe a more fruitful avenue would be to ask him to read an article or something manageable that takes our position on an issue and ask him for a reaction to it. But don’t push the issue in such a way that it damages your relationship.