critique:  Bitcoin is used by drug dealers and money launderers; therefore it is bad.

rebuttal:  Bitcoin has received a lot of press about criminal use, largely due to the novel darkweb marketplaces, such as Silk Road (now defunct), which used bitcoin as a key element early on. Yet, the fraction of total bitcoin transactions associated with illicit activity was never very high, and remains below 1% today. In fact, former CIA Acting Director Micheal Morell produced a report analyzing bitcoin's use in illicit activity and found that it's "significantly overstated", and is likely a far smaller share of the bitcoin economy than illicit activity done via the traditional banking system is vs global GDP.

The novel properties of new technologies often present criminals with opportunities before society more broadly finds use for the novel properties. In bitcoin's case, its uncensorable nature was a boon for darkweb activity. But this is also a key property of bitcoin that gives it its security and settlement assurances, and cuts out the friction and cost of middlemen that's evident in legacy money systems. This property also eliminates enormous classes of fraud - the kind that plagues credit card networks, leads to costly identity theft, and requires Visa and Mastercard to charge merchants ~3% of every transaction just to make consumers whole when fraud inevitably occurs. As with many new technologies, ultimately, the benefits vastly outweigh the downsides.