Searching for "US demographics collection nationalists" finds one result (your comment above - and presumably soon this one): https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...
I tried "US data collection nationalists" but that only found one page of results none of which supported your assertion: https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...
Do you have a better set of search terms?
The closest I've found is [1] which is a downvoted comment saying:
> Census data indicate White population has shrunk since 2010
Why is this the first bullet point? Why a focus on White people? Why do you care HN?
The only other place I see stuff like this is when it’s used as an alt-right talking point, or by white-supremacist mass-shooters who write about ‘The Great Replacement’ [1]
So that isn't even arguing against collection of stats. But it's the closest I've been able to find.
Perhaps you are misremembering?
And while people will surely respond to this post with "Ha, got him! He can't link to a specific example!", I don't believe it's a reasonable expectation of me to catalogue the thousands of comments I read on this website.