I believed you don't need to convince people to invest in bitcoin. Sharing them your knowledge and let them understand what bitcoin may help them is more than enough. Once they understand what you are doing the will invest if they really interested. But if not, let them be. Just respect their decision. Maybe bitcoin is not for them. Atleast in the end you knew for yourself that you tried to help them.
I completely agree with you. If a friend asks me whether he should invest money in bitcoins or not, my first advice to him is to learn about bitcoins first. I also tell them about the risks associated with bitcoins like the prices being very volatile. It is not right to show them only the bright side of bitcoins.
If you tell them that the prices are always rising and there is a correction after they invetrd, they will put all the blame on you. Monet runing my relationships is the last thing that I want to happen.