The argument the OP seems to be making is something along the lines of that CM has profited from thieves using their services in the past, therefore those wearing the CM signature should resign their positions if they want to maintain credibility when discussing ethics. (This is not my personal stance, but rather is my reading of the OPs stance).

I don’t think there is evidence that CM profited from the theft/hack in question by mixing the stolen coin. Given the amount involved, I think a competent blockchain analysis firm could reasonably track the stolen coin through CM.

To answer your question as to what can be done, additional confirmations can be required and analysis can be done to ensure any coin being mixed is not stolen. Given 200-300 confirmations, could blockchain analysis detect stolen coin? Yes, probably. Is this a reasonable request? No I don’t think so, but this is up for debate. As I mentioned, with the amounts involved, blockchain analysis should be able to detect the outputs of the stolen coin in question.

I think the benefits that mixers give, such as giving privacy for those dealing with moderate amounts, outweighs the drawbacks of mixers (the additional difficulty in tracking stolen and/or illegitimately obtained coin).