I agree that bitcoin is really for most millenials but not on the statement that it's for criminals. They are always magnifying that bitcoin is an evil tool for criminals but not considering that fiat is also used until today in ransom, drug trade and other terrible criminal activities.
Maybe millennials because most millennials knows how to use computers and since bitcoin is a crypto currency it will be more understood by millennials than other generations. Bitcoin being used by criminals are just made by some people. Even fiat currencies are being used by criminals on they wrong doings.