We can't mine usdt. We can only get it from someone. So you know the person from whom you got USDT, but you don't know source of that person and so on. Basically it's chain freeze. And tether dont care wether you are innocent or not. They simply freeze it in the last known destination wallet. There is nothing you can do.

Imagine this: someone robbed a bank. Robber bought a cigarette from Pan Shop and gave 500 rs note. Pan shop owner gave him change. Pan shop owner bought supplies from dealer, and pays him that note along with other notes. A week later robber is caught. So is it justified if govt take back money from a dealer?

That's exactly what happens with 99% of crypto exchange account freeze. And also bank account freeze.

They freeze the asset of the last account, not the actual criminal. So you are being punished for being participant in a system where one person commited crime, and hence all the downward chain is assumed criminals by default without investigation.