He isn't just a messenger. He wrote the article and the report.
The UN never quoted him. Western media quotes each other all the time. Information being regurgitated does not make it more credible. Similarly, telling a lie a thousand times doesn't turn it into a fact. The testimony seems to match up because the people giving the testimony keeps changing their stories. People already post fake and anecdotal evidence based on their own feelings.
You do realize the data he's cherrypicking is public information, right? You realize the document is literally on a Chinese government website that is available for you and I to download with a click of a button? Do you think it says "desired target" for "forced sterilization" on a Chinese government website? In case you're wondering, the "project expenditure performance target table" doesn't even mention sterilization. It mentions family planning, birth control, decreasing birth defects, reproductive health education, office furniture, computers, printers, mobile disk storage, air conditioning fans, medical equipment and devices, machinery, and family planning before pregnancy plus other free services. Did Adrian literally leave references thinking we're incapable of checking his sources?