If he is not a theological universalist he should stop claiming to be one. He should adopt a strictly racial religion of some kind. But to try to make of Catholicism (which at one time was dedicating to baptizing every single human being on earth) simply the utilitarian social mortar of "western civilization" is blatant nonsense.
Of course, I spent a lot of time yesterday re-reading Klassen and Oliver (yimmachu shemam vezikhram!) so I'm a little prickly right now. I found Oliver's atheism and belief in an ultimately meaningless universe a poor foundation for his racial crusade, just as I find it a poor foundation for leftist "social justice" crusades.
What is it about atheists and their need to crusade for things???
Pat Buchanan (who isn't an atheist) is expressing his views about the kind of country that he'd like to live in - one where people share his language, culture, etc. I don't see anything remotely sinister about that, nor is it contingent on anyone's religious beliefs or lack thereof. You can believe that the society and culture that you grew up with is worth preserving (especially when the alternatives are cultures of crime, poverty, and social dysfunction) whether you're a religious fundamentalist or an atheist, just as you can be in favor of smog-free air and clean drinking water whether you're a religious fundamentalist or an atheist.