The same goes you receive your salary from your employer, you never know it's from legal or illegal.
You guys certainly talk a lot about morals and ethics but you accept the payment that came from the commissions of someone who did the wrong deeds, Anything in your defence?
I disagree, AFAIK Chipmixer doesn't have minimum fee because they use pay what you want [1] means you could mix the coins and pay 0% fees. So they didn't get any profit/commissions from the scammer, unless the scammer want give a donation.
[1]
https://en.wikipedia.org/wiki/Pay_what_you_want