Does not in fact hunt down communists... today.
https://en.wikipedia.org/wiki/McCarthyism#Laws_and_arrests
See also Guantanamo Bay, Internment Camps, Lynching, etc.
It may not be the same today, but to think the US isn't above doing terrible things to those they are afraid of is to lose sight of our history.
It's shitty what is being done, but saying "Nope, we don't do that, but ignore the fact that we did it less than 100 years ago" isn't the greatest of moral arguments. Maybe better arguments, and better actions are in order.
The Chinese government has noted that Falun Gong is an active threat to their society and have strict laws.
Half the world has strange laws. Some places drugs can get you killed. Should a US drug-dog training company be sued for leading to the death of drug users?
Edit: What if it was a system to hunt down cults that the US has attacked, like those at Waco. Or that other countries don't tolerate, like Scientology?
That's possible because US tort law recognizes international laws to which the US is a signatory: if you commit a tort against someone, and the manner in which you do it violates an international law we recognize, the US quite sensibly recognizes the resulting tort claim.
Second: the US should prosecute this sort of thing, because otherwise the US will allow itself to become a haven for companies building technology to assist in "crimes against humanity". We have a spotty enough history with this as it stands. And, in the case of China, our local companies have enormous financial incentives to participate in this stuff.