[Izzy Dunne]

Non-Christian cultures have picked up the Western custom of putting up Christmas trees and giving each other presents, although they do not know why.

Not exactly.
The Christians co-opted the day from the pagan Yule celebration (winter solstice, Dec. 21) so as to assimilate, rather than confront them.

[egarvue]

I believe he's referencing cultures such as Japan, which do celebrate Christmas in some aspects as a gift-giving holiday. I had Veith as a college prof; he knows why the December date for Christmas was chosen. BTW, check out his most excellent book "Modern Facism: Liquidating the Judeo-Christian Worldview" if you want an excellent analysis of the modern plague of political correctness.