I really don't understand these arguments.
The law still applies whether or not you use cryptocurrency. Using cryptocurrency doesn't free someone from the consequences of their actions.
Illegal acts are still illegal acts.
What if they acquired the Bitcoin without using illegal means
Probably not possible in this case, but in DeFi where everything is ruled by smart contracts, what would make executing behavior allowed by those contracts illegal.
well the most obvious answer to that question is, we don't.