From my perspective, Bitcoin is not much different than US hundred dollar bills. If you've ever held one, in used condition, there's no telling how many illegal transactions might have involved it in the past. If run thru a scanner, it will most likely bear traces of illegal drugs. Is that the fault of it as a fairly anonymous currency (of course, a US$100 is not truly anonymous due to the serial number, nor is a Bitcoin transaction). Bitcoin is merely a new form of cash, usable for anything from the purchase of an automobile with all taxes paid to something ridiculously illegal.
I have little experience with the dark web, but from what I have seen (mainly gun sales), the sellers tend to stick to the letter of the law, no matter the form of payment. I've seen plenty of guns for sale for BTC, but they, just like USD-paid items, require legal delivery to a FFL (in the US) and an identity check upon pickup. I have no experience in the drug world, but from what I understand that would need to be shipped to the customer, providing an ideal opportunity for law enforcement to jump in at the time of pickup. I don't think at that point it would matter how it was paid for. And as for CP, that may be a more lucrative market, especially with privacy-enhanced altcoins and digital delivery.
So, is BTC inherently enabling for illegal operations? I think not, probably no more so than any fiat currency currently used for illegal activity. And given the scrutiny given to really large BTC transactions to fiat, I think it might even be less so.