I understand drug is a big market worldwide and fiat has been used since thousand years for drugs but is it really where you want bitcoin to thrive on?
Do I
want bitcoin to be used to buy illegal drugs - no, not really. However, do I want people to be able to buy whatever they want without a third party telling them what they can and cannot do - absolutely. Much like the famous quote from Evelyn Hall - "I disapprove of what you say, but I will defend to the death your right to say it" - I may disapprove of how people use bitcoin, but I would never dream of limiting their ability to do so.
This illegal things would have thrived without bitcoin as well, but bitcoin (and Monero offcourse) is making it smoother for them!
There you go. Scammers, money launderers, drug dealers, etc. all existed before bitcoin did. If bitcoin (and other cryptocurrencies) disappeared tomorrow, these people aren't suddenly going to become clean and go out and get jobs - the few who use bitcoin or other cryptos will just back to using cash or other fiat options as they did before.