Add SAG-AFTRA to the list of organizations that can't say "Christmas." The Fall/Winter 2018 issue of SAG-AFTRA Los Angeles (the newsletter of the actors union's Los Angeles local) has a "Calendar of Events" on page 7 that states:
Monday, Dec. 24 -- Office closed for holiday
Tuesday, Dec. 25 -- Office closed for holiday
Monday, Dec. 31 -- Office closed for New Year's Eve
Tuesday, Jan. 1 -- Office closed for New Year's Day
Now, which holiday do you suppose the office is closed for on Decembers 24 and 25. There's only one that fall on those dates. Christmas Eve and Christmas Day. So why not say it?
It's not like the newsletter was referring to the "holiday season." It was referring to two specific days that contain only Christmas.
And it's not like the newsletter is averse to mentioning other holidays. New Year's Day is specifically named.
The only reasons for SAG-AFTRA Los Angeles's newsletter to refrain from writing "Christmas" is that union leaders themselves find the word offensive -- or they fear that the word might offend non-Christian readers.
This is no oversight or trivial thing. The newsletter's editors certainly thought it was important to avoid writing "Christmas." They made a conscious decision to mention one holiday by name -- "New Year's Day" -- while simultaneously avoiding the name of another holiday -- "Christmas."