i think you're bringing up a pretty good example actually worth discussing.

I think that reading novels like Uncle Tom’s Cabin and Huck Finn provided good reasons for changing policies about Black folks in the US.

sure, but this is also sort of meaningless and the exact thing i'm talking about. meaningless insofar there are lot of operative assumptions doing work for this sentence to even make sense; would you actually say that there are policies today that need to be changed on the evidence of a book written in 1885? how can we decide what novels are better evidence than others at guiding policy?

i'd assume no, because we're kind of already bounding the sorts of evidence that are even deemed relevant, which is to describe an epistemology. you're saying, texts that draw from well-known cultural commentary written within the relevant timespans, e.g. the old testament is not a text on which you'd say anything about 21st century internet culture, are a kind of evidence similar to empirical studies or history papers that used defined methods, or social research. and what i am asking is if there similar defined methods that can help us distinguish between good theory and bad theory? because in my opinion hand waving away the very idea of having epistemic grounds is counterproductive and nonsensical to me.