But words — much as I don't love the fact in some cases (i.e. "impact," used as a verb; ick) — do evolve. Atheists say "goodbye," a contraction of "God be with you," and mean nothing of the etymological sense. Christians say "Thursday," meaning no reverence to the false god Thor. And on and on.
In this case, would you really argue that I am incorrect? That more than 1 in 1000 who use "Xmas" really mean it is a reverent nod to the Greek term Christos? And that the simultaneous yearly swelling of Christless Christmas traditions, and prohibitions of the mention of His name (or even the bare saying of the word "Christmas") is unrelated?
Some how, I get the impression that the Christless Christmas haters wouldn't even bother to use the term Xmas.