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:

Obama fails to remember he has another year where the military will be providing security and transport and the large majority of people in uniform are Christian. I hope every last one of them wish him “Merry Christmas”.
Seriously , is this true?
You really have to wonder.
Congress do your job??
so when is the military and country going to march to DC
Merry Christmas from an army veteran. F.T.W.
With religious overtones
Belay that order
One shot to his head is what comes to a lot of peoples mind. Christianity is the only reason he is still alive
Merry Christmas, Happy Birthday Jesus, may God the Father, God the Son and God the Holy Spirit fill our hearts and minds during this 2015 Christmas season and always. Merry Christmas to all Christians around the world. May the Lord Jesus Christ guard, lead and protect each and every one who trusts and obeys Jesus Christ. Amen.