The Obama administration has directed the military to not allow personnel to say “Christmas”, in spite of the holiday’s status as a federally-recognized holiday.
The reason given by armed forces officials is that not everyone celebrates Christmas and that out of respect for them, military members should refer to Christmas celebrations simply as “holiday”-themed festivities.
This prohibition comes in the context of a wider push for political correctness in society in general and the military in particular, as evidenced by the recent reprimanding of Navy Chaplain Wes Modder for simply discussing religion, as chaplains are wont to do, with military personnel.
See how servicemen have reacted to not being allowed to say Christmas at the link below:

Idiot
Just say it anyway
Merry Christmas to our Military and to the United States. Sorry that the idiot in the white house is so ignorant
F*ck the black muslim animal Merry Christmas to all our troops
Merry Christmas Mr. President.
Obama is no longer Commander in chief,per executive order of Congress.
Resign Obama, you in NO way represent this country or what we stand for. GOD BLESS AMERICA!
Merry Christmas to our military
stupid.
He’s getting desperate.