But I suppose a counter argument is if higher criminal "economic importance" would cause more human rights violations than were prevented. So, indirectly, you may be right.
The difference is the banks have the coercive power of the state to protect their actions, with bitcoin, as it is an inherently illegal operation, there is no power to force people to interact with dishonest users, the dishonest types you seem to be pointing out, would shy away from a market that do not have a coercible market advantage...
So it's necessary to differentiate between dishonest activity at the level of the currency (e.g. inflation, interest), and "normal" dishonest activity which utilizes a currency in an honest manner, but to trade dishonest produce or services - e.g. buying drugs at market value. Bitcoin will be supposedly immune to the former type, but will greatly liberate the latter from the chains of state control. We might expect, for example, significant organized crime in a bitcoin world; but we're just coming back to a political argument here - anarchy Vs state, and there are other threads for that.