Personally I don't think it's necessary to prove to people about bitcoin and as a matter of fact, bitcoin did not ask you to run a campaign. The question is what are the prove you're going to give to them about bitcoin, That it has a good potential in the future? It's true that bitcoin has a good potential but we don't have to be too sure about it or trying to give a guarantee that they will succeed If they invest in bitcoin, for me bitcoin investment is just like those normal investment we do the difference is just the volatility and the time it takes before you can actually profit from it.
That's it, I also personally don't think there is any need to prove Bitcoin to people. However, those who are not greedy and don't want to earn naira from Bitcoin investment in a very short time and want to know about BTC, it may be possible to inform them about the growing potential of this currency. Here the OP's friend himself fell into the trap of fraud and later after losing money he became adamantly against BTC and he doesn't want to pay attention to anything related to Bitcoin, so even if we explain the immense potential of Bitcoin to this person, he will not understand because his mentality is against BTC. Overall, we can explain to these people that Bitcoin investment is like a normal investment but there is volatility involved and there is a long wait to get the naira or yield.