That doesn't really have any bearing on whether or not the National Review is a broadly racist newspaper.
Look at former racist house representatives who were Democrats but renounced their racism. It's as if they never espoused racist views. But if they had been conservatives, then by definition they could never disavow their racist past and would for ever be racists.
It would be silly to say the DNC is still what it was in the 1950s, since "organisations change and it was 60 years ago" but the comment you're replying to is arguing that we only give that sort of benefit of the doubt when it's convenient politically. Buckley wouldn't be relevant otherwise here, and every single "older" newspaper would be a conservative rag if we were to go by what's been published or said by their founders.
But it’s still not clear what this has to do with the National Review.
[1]: https://en.wikipedia.org/wiki/William_F._Buckley_Jr.#Views_o...
[2]: https://en.wikipedia.org/wiki/National_Review#Controversies
The examples in that list of controversies are weak to say the least. In each case that could vaguely be considered racism or antisemitism, the higher ups at the magazine issued a rebuke and often dismissed the writer. Is this really all you got?
Meanwhile, the NYT posts shit like this: https://www.nytimes.com/2017/11/11/opinion/sunday/interracia...