Ad hominem, and not persuasive.
Just because it’s an ad hominem attack doesn’t mean it’s a fallacy. If people were saying “Zenz has never bowled a 300 in his life, and you trust him about China??” then it would be, but Zenz’s history is relevant to describe his motivations, especially given that he is often the sole source of the accusations.
The difficulty with anything around the Uyghurs is that leftists are tasked with proving a negative; we can point to the lack of direct evidence (no bodies or refugees, even), but libs just use this as evidence of China’s oppression (parenti_quote.jpg). I think a better strategy than just “read the fucking papers” is to relate this to the WMDs in Iraq. There, we had a complicit media reporting on completely fabricated information about one of America’s enemies - it even includes a Pulitzer-winning expose where reporters annotate a bunch of blurry satellite images as evidence.
Yes it’s an ad hominem. You’re saying he’s an untrustworthy source without examining any of his arguments, that the definition of ad hominem. And it’s lazy.
Your example is a non sequitur, not ad hominem.
You don’t have to prove a negative, just demonstrate that the evidence for the affirmative is insufficient. But that means reading so it’s hard I guess.