Maybe those who do this can manage to evade prosecution for a while, but if their identity is exposed, they are going to be subject to the draconian penalties any drug dealer faces, including life imprisonment or (in some jurisdictions) the death penalty.
Compare to those who currently distribute things like BitTorrent software. This has legitimate non-copyright-infringing uses, and the current vendors of such products studiously avoid the kind of stupid rhetoric you hear out of people pimping their drug sites.
Compare to Napster, which openly participated in copyright infringement and was easily shut down. But then compare to the P2P stuff that followed like Grokster and Limewire, which sold software with legitimate uses, but also spouted all kinds of dumb rhetoric and had internal emails showing that they too were basically encouraging copyright infringement. They too were held liable.
The common thread in all these busts is site operators dipping their hands into the pool of tainted drug money. Once they did that any rhetoric about freedom is basically just bullshit. They're just drug dealers like any other at that point.
The only kind of site like this that stands any chance of withstanding legal scrutiny and/or prosecution is one that does not explicitly exist for illegal purposes, and also doesn't basically act like a bank of sorts, subjecting it to financial regulations. If one legally provides a service with substantial legitimate uses, and it just happens to be able to be used for illegal purposes, and does not oneself participate in those activities, that is always going to be a good defense.
I think OpenBazaar fits the bill quite neatly. The dev team's publicly said that they dont intend for OB to be used for illicit trade, but cant stop users from doing so.