Crptocurrency is bad to those people who know nothing about this because of the risk. Bill Gates might right but we have our own opinion and if you think you are confident enough with this then go for it after all those big guys will use bitcoin soon and promote their own coins.
So you're telling me 1) If you know about cryptocurrency then it's good for you; 2)Bill Gates doesn't know about cryptocurrency, he's nothing special in IT and doesn't understand anything; Right?
So: 1) Cryptocurrency ain't bad or good, it's just a tool; 2) Mr. Gates understand everything, he just see the obvious thing that nowadays cryptocurrency are mostly used for fooling people so he want to warn people they can lose their money