Earlier quoted context omitted.
"Taking away" is interesting language. The ability to transfer money without either meeting in person (meetings can be surveilled) or generating records subject to disclosure (shell companies and laundering schemes can be deciphered through forensic accounting) is unprecedented. We've never lived in a time when people had cryptographic certainty of the secrecy of their transactions.
Cash and dead drops provide both of those properties. There are many other ways to investigate crimes. Just because the internet is new doesn't mean that human rights don't apply for this new communication medium.
Cash transactions carry substantial risk: both parties must be physically present in some place to make the deal. They can be tailed, the meeting place can be under surveillance, they can be raided, they can murder each other and run, etc. It's also impractical to deal with large amounts of cash due to the risk of robbery/theft (including civil forfeiture), and legitimate entities won't take suitcases full of cash for large purchases. Infiltrating and exfiltrating large amounts of money from the legitimate banking system is also very likely to leave traces that can be understood by sufficiently skilled/motivated forensic accountants.
Whereas flipping some bytes in the firehose of cryptographically secure bytes already coming in and out of every home is undetectable and basically risk-free.
Some much more concrete human rights are ensured through taxation: food, shelter, water, health care, police, education, national defense, etc. If you make taxation effectively optional by running a perfect, free money-laundering system, some of them may have to go.