There are a number of reasons why this kind of blacklisting is problematic in practice, but take it with a grain of salt, because I'm the creator of Wasabi, so I am biased.

• This Elliptic report identifies 0.65% of all Bitcoin transactions are mixing transactions. This means, if that kind of blacklisting would happen, they would have to blacklist most bitcoins in existence.
• The same report states, 50% of DNM users don't use any mixing, but directly send to exchanges (mind blowing, I know) and these are the coins being blacklisted.
• From another point of view, Wasabi's anonymity set will be constant 100, and if a coin from it is tainted, would they really blacklist all mixed coins, where every coin has exactly 1% chance of being the tainted one?
• The user base of Traditional Bitcoin Mixers is limited to a certain type of user, who is in desperate need of privacy and in order to get it, he is willing to risk losing money. Since coin loss, and other issues are architecturally impossible with Wasabi, our target user is not limited to them, the target user of Wasabi Wallet is everyone, because everyone needs privacy.
• If someone is extremely paranoid, he can just spend coins to himself a couple of times before sending it to the desired "legitimate" place. This is what Samourai's Ricochet is doing.
• Speaking of legitimacy, zkSNACKs, the company behind Wasabi is a legitimate company. Privacy is not only not a crime, but a fundamental human right and if an entity would blacklist a mix output, they would be looking ahead of legal trouble. If such a thing would ever happen, please notify us.