If you read past that next sentence, I admitted it won't actually cause such activities to completely cease. It just needs to be stunted so that the majority of such transactions are disincentivized.
Disincentivized enough that nobody would bother adding it to their retirement strategy or use it out in the open. The dark web will continue to do their own thing.
Lol.. and that will stop all crypto-world currency trading? Just like how making drugs illegal stopped all drug trade?