I think he needs to read about a low information diet! I know the temptation to get into FB arguments - my spouse added the wife of his HS friend to my acct (because the husbands don't do FB!) and she's about as pro-Trump as you can get. So...I lasted a week before I had to snooze her for 30 days.
You might want to ask him what he gets out of it? Does he think people are reading and caring? Does he take religious posts personally? Because it can feel that way. All of a sudden there's this "bubble" (pro-Trump) in my feed and it feels like a personal attack. And...it's not. I chose to disengage, rather than start arguing with a very nice woman who I met exactly once.
Is he lonely? Because the "good" thing about social media is that it gives you a connection. I keep in touch with family on the other side of the country and even in other countries, much more easily than ever before. When you feel like the oddball out, it's nice to find others that you have things in common - running, crafts, healthy eating, scrapbooking, muscle cars, hiking, motorcycles...whatever your interests may be. (I grew up as sort of a weirdo smart kid with few friends.)
And all I can think of is that...man, I read the sentence about the old guy and his Facebook problem, but he's not that old - same age as my spouse. If it makes you feel any better, my husband basically works, does stuff around the house, and hangs out with the kids and me.