It’s extremely easy to disprove this with facts about how the Bitcoin protocol itself works, along with data we have on how much of Bitcoin’s usage is on criminal activity.
Let’s get the straight up numbers out of the way first. Right now, only about 3% of the activity is possibly from illegal activity and it’s decreasing every day.
It’s always been a myth that (Layer 1) Bitcoin is the most private way to transact, while you technically can’t see who exactly made a transaction written on the blockchain, the entire history of Bitcoin including all transactions are on a PUBLIC ledger. That’s why criminal activity is moving onto privacy coins.