When I was eight years old or so and first took note of the phrase 'Merry Xmas,' my piety was offended by what I took to be the removal of 'Christ' from 'Christmas' only to be replaced by the universally recognized symbol for an unknown quantity, 'X.' But it wasn't long before I realized that the 'X' was merely a font-challenged typesetter's attempt at rendering the Greek Chi, an ancient abbreviation for 'Christ.' There is therefore nothing at all offensive in the expression 'Xmas.' Year after year, however, certain ignorant Christians who are old enough to know better make the mistake that I made when I was eight and corrected when I was ten. See here.
It just now occurs to me that 'Xmas' may be susceptible of a quasi-Tillichian reading. Paul Tillich is famous for his benighted definition of 'God' as ' whatever is one's ultimate concern.' Well, take the 'X' in 'Xmas' as a variable the values of which are whatever one wants to celebrate at this time of year. So for some, 'Xmas' will amount to Solsticemas, for burglars Swagmas, for materialists Lootmas, for gluttons Foodmas, for inebriates Hoochmas, and for ACLU extremists Antichristianitymas.
How could an ACLU bonehead object to 'Xmas' so construed? No doubt he would find a way.
Merry Chimas to all, and to all a good night.