People usually have negative thoughts about everything outside of their knowledge.
You friends are kinda right about bitcoin.Was it used in the deepweb(or darknet) to buy illegal stuff?Yes,it was.Is bitcoin a scam?Hmmm,who knows?What if bitcoin is just the tool used for the biggest exit scam in the entire financial history?I'm not hating on bitcoin.It's just a different point of view.You have to know and understand the point of view of your friends.