"None of my ancestors were Christian"

Somewhat unlikely, actually, if I read my Alex Shoumatoff correctly. (And if you haven't read The Mountain of Names, that grand overview of geneology and our misconceptions about it, run out and do so.) As the "tree" of our ancestry broadens, doubling with each prior generation, the odds of some of our ancestors--quite possibly through an unacknowledged liaison--being members of quite surprising and "foreign" groups grows very large.

My mother's mother was born in Toronto, of parents who'd recently moved to Canada from St. Ives in Cornwall. For centuries, St. Ives was a hotbed of smuggling, notably of wine and other goods from Portugal. The chances that some of my ancestors were Portugese are very large. The chances that some of their ancestors were Muslims, or black Africans, or even both at once, are similarly considerable. (Or, for that matter, Jews.) This kind of thing is true of most people, save for the immediate scions of extremely isolated populations -- and I definitely don't mean "isolated" in the Hasidic or Amish sense, since those kinds of "isolation" are notorious for creating exactly the sort of, ahem, undocumented liaisons that make geneology such a speculative pursuit.

None of which robs anything from the points you're making to this fellow. As you know, Bob, I'm arguing in order to be polite.