One of the many great joys of being a person of faith, no matter what faith, is that your faith is never negatively impacted by anyone who doesn't share it with you.
You can work beside people who don't share your faith, live next door with people who don't share your faith, rub elbows in any variety of ways with people who don't share your faith, see representations of other faiths on display, even in public places, and none of this has any negative impact on your faith. Your faith is YOUR faith. If you are comfortable in your faith, you may share it with anyone who wants, but you don't have to force it down anybody else's throat and nobody else's faith, or lack of faith, diminishes or challenges you. You may pray for others who don't share your faith to "come on board," but when you are comfortable in your faith, you do not threaten anybody else's faith, or lack of faith, nor do others threaten you.
Therefore, Merry Christmas to all, no matter what your faith or even if you have no faith. I say this based on my own faith and the joy I get out of wishing all a Merry Christmas. If you wish to say "Happy Hannukah" or "Happy something else" to me, based on the joy you feel from sharing your own faith, I welcome your joy into my own heart and and say "right back at you."
If you are not a person of faith and still enjoy the joy that fills the Holiday Season and wish me "Happy Holidays," I welcome that expression, too.
All expressions of joy and good will should be welcome at all times of the year, Christmas Holiday Season included. Positive expressions of joy and good will should also be welcome any place where people wish to place them, and yes, that even means public property. I don't want government employees required to work on building or even maintaining such displays; but if individuals or groups wish to put up displays celebrating their faith and their joy in their faith, or joy in having no faith, for that matter, even on public property, that will be fine with me.
What I don't welcome is attacks on anybody else's faith. We can celebrate our own faith, or lack of faith, without attempting to desecrate or otherwise put down someone else's faith or lack of faith. However, there is no reason to be "offended" by someone else's expression of their faith. What is offensive is displays that put down someone else's faith.