Usually people say negative on things that they don't understand and for sure that they would realize their mistake later on after Bitcoin continue to succeed. Same thing happen before on where Bitcoin doesn't get much popularity way back then. Many people call Bitcoin as scam or ponzi schemes due to its volatile nature and other negative things they notice. But for many times Bitcoin has proven that its not and those people said negative about it before became an investor now.

If they are still fearful despite of positive situation and advices presented then let them feel that. For sure that later on they realize that they commit a big mistake for ignoring Bitcoin especially when it pumps and reach new level not only with price(ATH) but also with adaption reached globally.