Yeah we can deny that many crime and dark transaction made with bitcoin as a payment.
But, if people adopt bitcoin as a mainstream payment, i'm sure it will really make everything faster and easier
Well, there is no need to deny since there is a lot of them in the past, I don't know how but all I know is that it is still not impossible. If I can remember correctly, some say that the reason why Bitcoin is booming is because of the fact that there are a lot of people use it to transact payment in the deep web. All I know is that we can't stop people from using Bitcoin in illegal transactions and if someone uses Bitcoin to scam, it is not Bitcoin's fault, it is the scammer's and yours.