There's no dangerous precedent/slippery slope - in the financial world offering a money transfer service to anonymous customers is already banned, that's what KYC/AML laws are intended to do. There's no right to trade anonymously and for large transactions legitimate businesses are required to identify you and not accept anonymous customers (KYC requirement).
It doesn't necessarily mean prohibiting anonymous instruments like physical cash or Monero, but it means that any non-small use of such instruments is required to be accompanied with documents about the transaction.
E.g. you can legally sell stuff for a briefcase of cash, but you're required to declare the transaction, including the identity of that person (e.g., in USA, IRS form 8300 for cash amounts exceeding $10000; you can legally sell stuff online for Monero or whatever other consideration, but if it's a significant amount, then you are required to identify the person even if the payment instrument is anonymous.