USD has a much better ratio of legal to illegal transactions. If cryptocurrency had anywhere close to that ratio it would be a lot easier to support.

However, in general, I am not a big fan of banning things. I hope that the damage that cryptocurrency is causing can be reigned in without banning it, though I suspect that cross-border jurisdictional issues will make that hard. Ideally, the cryptocurrency community could come up with internal solutions to limit abuse, but that seems unlikely given current trends in that space.