Without drug trading sites there would be no Bitcoin
I don't think that's true, but the black market use did help and quicken its rise, and the publicity - good or bad - from the use on Silk Road etc did bring it into the mainstream's attention.
This is exactly it. Any publicity is good publicity. All we need is the mainstream's attention, and the benefits of cryptocurrencies will become self-evident.
Well, silk road and other illegal market did have an impact on bitcoin and cryptocurrencies as such. However, I dont believe that they would be useless without.
They simply improved the velocity of crypto growth.
Also true. Without Bitcoins use in SR it definitely would've had a slower growth.