3. Anyone clear in its head wouldn't use it : First, he doesn't recognise any kind of manipulation of the money and the danger that there is for people keeping all their savings in fiat. I know that because I had him as a teacher too some times ago. So trying to explaining him about the fact that there is a clear war against cash and evident facts, like that that shows our money need to be converted into something viable to be protected from massive surveillance, is useless. Him not understanding that, since its the best argument I have, I couldn't have replied. When she told him about the speed of transactions, he replied "we have PayPal", so I said me that it wasn't worth to ever try explaining anything. As a final point, he said again that the sole real use that is making standing apart is that you can buy drugs on the Internet
It all depends on the purposes of using Bitcoin
If Bitcoin earns you decent profits, then I would rather say that everyone clear in his head should use it, even if for getting this easy money only. Sometimes, well, actually often times, you should be quick on the trigger so as not to lose an opportunity suddenly coming up. It would be interesting to see if he himself would ignore a sure chance of earning some bucks. Otherwise, nothing is perpetual, and how we deal with that is what ultimately matters