Just give up, never try to persuade thing that other person don't understand, everything comes by time, you only can suggest that to do, but if that person can't understand that you want, give up...
I agree on that. You can not make someone do the thing you want them to unless they themselves understand about it. You shouldn't force someone to do something they don't feel like. Talking about bitcoins many people don't know about and quite not interested but with time they will eventually have to deal with it.
It will have to come from them self, giving them bitcoins maybe the wrong approach. It would be better to let them experiment with bitcoin.
When they like it, they will buy it themself.