Crypto industries not really dangerous bit it's been associated to scam, deep web and other illegal internet transaction and money laundering by those who don't really know what crypto is all about. It's an old myth that been use to frighten people to get involve with crypto.
Many countries banned them not because they are really dangerous but because it' unregulated and they can't control crypto. Also, it's non taxable coz they can't monitor them so they opt to ban it.