If these are illegal, then you're not really presenting a counter-case that darknets are only useful for illegal trade. If they're not, you don't need a darknet to get them.

> If they're not, you don't need a darknet to get them.

False. Some things are restricted by abuse of power, not by law. For example, it's very hard to massprint antiputin agitation in Russia despite there is no law against it.

Fair enough.