For years, now, this greeting has been controversial. Some see it as elitist- certain religonists putting themselves above others. Others see it as exclusionary- Those who use this greeting not acknowledging other religions.
As one of those "certain religionists," I don't see it that way, exactly. I can see the other POVs, but that isn't my own POV. I don't use this greeting for the express purpose of elevating myself and degrading others. I don't say this to deliberately make others feel left out or ostracized.
I use it because it's what's in my heart.
A while back.. about 2000 years (give or take) ago, a baby boy was born. As an adult, he did some amazing things- transmutation (water to wine), raising the dead (repeatedly- Jarius' daughter, Lazarus), healing diseases of body and mind (too many to mention), feeding thousands (twice), and commanding and controlling the elements (the storm on the Sea of Galilee).
But all those, as amazing they were, were not the greatest of His miracles. The greatest miracle Jesus performed was done in the quiet of a private garden, late at night, while His friends were crashed out on the other side of the garden.
In that Garden, He made recompense to the natural laws of justice for every wrong committed by every human being ever born- past, present-future. Every horrific act, every lapse of judgement, every frustrated outburst- He made it OK. He experienced the full width and breadth and depth of human experiences, every joy and sorrow, every pain and pleasure, every sickness, fear, frustration, hurt, embarrassment.
The second-greatest miracle he performed was a couple days later, when, after His death on the cross, He rose from a borrowed grave. Again, this was done alone, in private, without an audience.
The reality is, I say "Merry Christmas!" because Easter. Without what He did that last weekend, nothing else matters. "Merry Christmas!" is an expression of gratitude, joy, and hope! It's something we "certain religionists" want to share.
So next time someone says, "Merry Christmas!" to you, remember that they're really saying, "I'm so grateful for my existence, for my God, for my Savior. Oh, that I were an angel, to let the world know!"