Oh they've been sued and lost [1]? Maybe not that one.
[1]: https://apnews.com/article/sandy-hook-school-shooting-reming...
It doesn't have to be used for money laundering, and even if using it to move funds anonymously, that doesn't mean you're money laundering. There are good reasons to not want individuals and state actors whose jurisdiction you're not under to track your financial movements, even if you are reporting your income accurately with your own government.
The whole point of tornado cash is to "pool" funds to obfuscate who owns what. If your funds get "pooled" with funds from a criminal enterprise, then you become an accessory to that crime. Good luck using your hypothetical to convince a court otherwise.
"I didn't ask where the (other) money came from" is no defense.
Regardless of how you feel about it, you can’t deny that they were doing something illegal under US law, and a consequence of that is that the Feds can come down on you, even if the law seems ad hoc and unfair.