Crypto has the same value as every other fiat currency in the World...so essentially your question-for me at least-boils down to how can we ban every fiat currency in the World?? This includes the Norwegian Krona, the Hong Kong Dollar, the Swiss Franc and the Deutsche Mark. I am baffled as to why you would either want or need to do this. You can simply not use crypto...or credit cards or money orders or wire transfers. All of which, at one time or another, were used by bad actors to commit crimes.
If someone had banned them before they had a chance to establish their users and use cases, it would have been just as silly as someone banning cryptos before they find their uses and use cases. Not everything is needed everywhere.
I am more concerned by the apparent rigidity of thinking surrounding what is merely a new method of paying for things, documenting things and file transfer etc. I keep seeing "techie" people BASHING TECH. And I am astonished. And very amused. It seems so silly to watch some folks who should obviously be on the side of reducing costs, speeding up transactions and opening markets...be so afraid of tiny bits of computer code. Especially when some of these same folks don't pay near as much attention to the damage their own coding can cause their customers.
It makes me think that very single tech person who has bashed any crypto anywhere who also codes....should have their code examined very closely for signs that it conforms to values they now choose to claim they hold. To wit...unless it's perfect, it shouldn't ship. Cryptos aren't perfect, things will happen. But if you are apart of the community that until cryptos came along, got ignored, couldn't get loans, couldn't get fair valuations of property, mortgages, send money without it costing the Earth or pay bills without buying a money order etc or earn fairly distributed interest on your savings, then cryptos-warts and all-are a GODSEND. A chance for the rest of us to finally build a financial platform for ourselves and those we care about...without worrying about high theft fees from Wall Street...or not being able to fulfill our potential because someone values us at less than nothing.
And I can't imagine why anyone would want to ban THAT.