From my point of view, it labelled as dangerous and banned by goverment because they can't control it. It's about power, anonimity and uncertainty. Cryptocurrency does not have a single rate like fiat money, the rate can even change several times a day. And then because of the anonimity of the cryptocurrency, it's easier to used on black market. Money laundry, scams, deep web stuff, and even worse stuff that we couldn't imagine. Thats why Goverment see it as a threat, I guess.