I.e. how would you convince European citizens that it's right to sanction Chinese businesses that profit from prison labor, but wrong to sanction US businesses that profit from prison labor?
Or ignore those Europeans ... how do you convince US citizens of it? Sounds like they're quite angry about the domestic problem right now.
The problem becomes more obvious when you look at incarceration rates in the US. Of course, the US says "that's not racist, they just commit more crimes". And we (as in "Western societies") tend to believe that because the alternative is uncomfortable. There's a pretty vocal movement in the US that disputes that claim and alleges that the fact that wealthy and powerful people profit from prison labor is responsible for a) the rate of incarceration in general and b) the differences in incarceration rates.
I don't know whether they are right, but once you start going down that route, you better be prepared to walk for a while. If you don't (that is if you treat the Chinese behavior different from US behavior), you're going to do more harm than good, I believe, because people will understand that your talk of human rights is just a weapon in economical/political/military conflicts, and not a principle you believe in.
The whataboutism you're trying to push into the discussion isn't leading anywhere. I'm sure you'll find plenty of opportunities to discuss the US prison system, but this isn't one. Here we have people who have wronged nothing being labeled as extremists and then put into concentration camps.