I'm not sure this argument holds much weight. All investments have inherent risk. It's the job of the investors to assume how much risk they're taking. You cannot ban all digital currencies simply because a large amount of ICOs are poorly thought through, if not malicious. That would block a huge amount of innovation in a technology with huge potential to revolutionize many markets, if not all markets.
It's the equivalent of banning startups to protect investors from stupid/malicious founders, which has obvious negative effects on the economy. And with crowdfunding making its way to startup investment, it's not a reach to compare the two.