Does he have children and/or Biblical values?

I think that was what finally worked for me, was realizing it's lasting, its a finite supply, and it's going up long term, so will at least make a good inheritance for my children. (Proverbs 13:22)

Even if you don't understand it, do it for your children, long term view, which also separates it from all the alt coins.

Pointing out that a small amount now could make a huge difference in their lives. That might get him in the door and like others have pointed out, once you have some, you are more inclined/motivated to learn about it.