Bill Gates said that is not without reason, there is a good reason too.
In an interview, Bill Gates said that the anonymous nature of blockchain technology as a basis of cryptocurrency could have a very bad impact.
"The main feature of cryptocurrency is its anonymity, which I think is not a good thing because it can provoke more crime, terrorism, and tax breakers," he said.
In addition, the utilization can also give a very horrible effect for users, one of which is losing his own life.
"Currently, cryptocurrency is used to buy fentanyl (a type of pain relievers) and other drugs, so it can be said this technology can cause death indirectly," he said.
Bill Gates as a HUGE technological innovator, that's a very ignorant thing to say though. He sure does well know every single technical advancement has it's own disadvantages and sort of "loopholes"
(for a lack of a better word) that could be used in a negative manner
(e.g. computer/www for stealing money, identities, etc).
And I think people who buy drugs and other illegal stuff uses Monero anyway.