Maybe you approach him in a wrong way just tell him that its like a social media where he can discuss certain things about cryptocurrency.
Also maybe before first you introduce this forum to him maybe try to see first if he is interested with crypto since if not your teaching or advices will just turn into waste because at the end of the day he will just say that crypto or this forum is a scam again. Select those people who show interest about crypto since they are the one who will listen to you and follow you to learn more about it.