Not true. The X in Xmas is to use the X as a representation of something else, like it does in mathematics. The purpose it serves is to shorten the number of letters used to spell out Christmas in full.
X is a symbol for the Greek letter Chi, which is the first letter in the Greek form of the word Christ. Abbreviations, dating back many hundreds of years, may have written Christmas as Xtemas or Xmas. They specifically reference Christ, and are by no means a way of commercializing Christmas or minimizing Christ's importance. As an abbreviation, when people wrote the term, they usually still pronounced the word as Christmas if they read it aloud. It was simply a convention that could speed up writing that was used as far back as the 11th century. Xmas isn't the only abbreviated use of the word Christ. There are other derivatives like Xtianity and Xtian (Christianity and Christian) that have been used by various writers for centuries.http://www.wisegeek.com/what-is-xmas.htm