I’m not sure how you’re interpreting these, but if you are against businesses deplatforming those who express neonazi, and white nationalist propaganda I don’t think Paul Graham’s message supports you.
I doubt Paul graham equates neonazi propaganda with his examples of past situations where you could believe something that was later thought of as very wrong: “ how can you be sure you wouldn't also have believed everything you were supposed to if you had grown up among the plantation owners of the pre-Civil War South, or in Germany in the 1930s”
Are you saying that in 30 years that society will collectively think neonazi beliefs are correct and thus we were crazy to ostracize them? And you are saying that is why we should stop censoring them? Because in a future state we might live in a dystopia we should stop censoring the people trying to create the dystopia? And also that censoring neonazis is akin to those example like being anti slavery in the antebellum south? Is this your take away? Those arguments sound rather farcical and Paul himself actually explains why that is.
Paul says this: “Of course, we're not just looking for things we can't say. We're looking for things we can't say that are true, or at least have enough chance of being true that the question should remain open.“
There is no doubt about neonazi propaganda. Whether or not it is true is not an open question. White supremacist propaganda maybe being right is not an open question.