If the West wants to influence internal China policy, it needs either a clear moral high ground for Chinese citizens to refer to, or clear economic upper hand. It doesn't have the latter right now (maybe never will again), and as this thread demonstrates, it doesn't have the former either.
Re: open discourse and changeable policies, China policies are more changeable than you would gather from the cartoon picture in Western media. They change constantly, in response not only to public opinion (as expressed on the internet these days), but also in response to continual internal debate within the CCP.
The US, for all its waving of the "free speech" banner, is only as changeable as the culture allows. Right now, for example, there would be no hope of reforming either prisons or e.g. a climate policy that might destroy civilization itself, because ~50% of US culture believes those aren't necessary.
Also note that open discourse is only allowed to a certain extent, as seen in surveillance and countermeasures against protests and organizers of any kind, from 1776 until the present day. So we can't in reality claim to be a society of free discourse when it comes to threats against the status quo, perceived or otherwise.
Prison labor in the US is only voluntary if people choose it over labor outside of prison. The fact that people sometimes choose it over staring at a wall for decades (and, one can imagine, being harassed by prison staff for not making the place more profitable) doesn't make it voluntary.
And finally re: Muslims being forced into labor camps against their will. It was not a century ago that the West dealt with its Muslim-extremism problem by bombing cities and weddings, and causing the economic collapse of entire countries. You want leverage over Chinese policy, you need to address this first.