We are talking about an entity that according to the treasury has laundered more than 7 Billion USD, assisted criminals and neglected complying to Anti-Money Laundering/Countering the Financing of Terrorism (AML/CFT) obligations willingly and repeatedly. Tornado Cash has repeatedly failed to impose effective controls designed to stop it from laundering funds for malicious cyber actors, regularly and without basic measures to address its risks.
This according to the treasury goes on for years since its creation, so everyone who actively contributed to the entity is considered a threat to national security and often, if you look at the sanctions list of OFAC sanctioned entities, rightfully so.
Retroactively, and to my knowledge, there is not a single investigation and OFAC sanction that got lifted by a court because the accusations themselves were wrong. And it's not like you don't have the right to appeal those sanctions. Entities and sanctioned people quite often do so, and fail.
See https://www.cadc.uscourts.gov/internet/judgments.nsf/C2B2FFF... for example.
Tornado Cash is not just a foreign electronics company that stumbled into an OFAC sanction because it accidentally sold a Toaster to Kim Jong-un, so he can enjoy a crispy morning toast.
Where you are right is, that OFAC sanctions are a significant impediment to commerce because you cannot predict who will be sanctioned in the future. That's why, as a company or even individual, you need to do due diligence on who you get in business with.
If you import fruits and someone gives you 5k per box of Avocados extra to import them from Mexico to the US asap, you can bet there are not just Avocados in those boxes. You can pretend you didn't know, but if you don't want to end up in jail for providing service to a cartel, you need to make sure there are only Avocados in those boxes and the premium is for extra fast shipping.
Everyone knows that virtual currency mixers are commonly used by illicit actors to launder funds, especially those stolen during significant heists. This is at least common knowledge since the Silk Road days.
So if you contribute to such a project, that has the potential to harm your fellow citizens and contribute to financing of terrorism, without making sure it is complying to Anti-Money Laundering/Countering the Financing of Terrorism (AML/CFT) obligations one hundred percent, you can't just cry foul play and say I didn't know anything of this. Especially if you understand code and the inner workings of said project or have a direct line to the people in charge if you frequently contribute.
So, in my opinion it's more than ok if everyone who contributed to Tornado Cash and enabling it to do what it is accused of, their life should turn to sh*t immediately and everything they touch from here on. Because getting people harmed or financing terrorism or foreign state actors is not a trivial offense. Laundering virtual currency for criminals hurts real people.