Honestly, it is not a good idea to try to convince anyone to invest in Bitcoin. I don't see any reason why someone would try to do that. The best approach is to introduce Bitcoin to them and allow the knowledge they gain about it to convince them to invest. As you said, if they fail, they will fully blame the person who advised them to invest. It's better to avoid anything that could later bring blame to us.
As we all know, Bitcoin involves risk due to its volatile nature. If you try convincing someone, they may go ahead and invest money they might need in the nearest future or even borrow money to invest, which is very risky. Because may need money at a time when the price of Bitcoin is down, and they might end up selling at a loss. There is also the possibility of getting scammed by scammers. Convincing someone to invest can lead the person to make a wrong decision.