This topic makes me laugh. I tell Christians that their God opposes the practice of Christmas. I point them to:
Jeremiah 10:1-5
Hear ye the word which the Lord speaketh unto you, O house of Israel:

2 Thus saith the Lord, Learn not the way of the heathen, and be not dismayed at the signs of heaven; for the heathen are dismayed at them.

3 For the customs of the people are vain: for one cutteth a tree out of the forest, the work of the hands of the workman, with the axe.

4 They deck it with silver and with gold; they fasten it with nails and with hammers, that it move not.

5 They are upright as the palm tree, but speak not: they must needs be borne, because they cannot go. Be not afraid of them; for they cannot do evil, neither also is it in them to do good.

Christians ignore this because apologists say this isn't about Christmas even though they're doing exactly what God says not to do.

I proudly proclaim "Happy winter solstice celebration!" which flies right over the head of most Christians.

Even as a kid I preferred to say happy holidays as it covered all the holidays around that time of year without having to mention every single one. I enjoy using the term even more in recent times, just to see if it irritates any paranoid delusional cranks

I usually say happy dead guy on a stick day,their reaction is priceless. Lol

I say it to exclude my self from Xmas and the hole Jesus bla bla bla. But when they try to correct me. Then i say it again just to spite.

As an introvert, I avoid talking to other persons.
If they say Merry Christmas, I say it back.
If they say Happy Holidays. I do the same.
...Hail Satan...Sure, why not. lol

For my older family members, I stick with 'Merry Christmas'. For my pagan friends, it's 'Happy Winter Solstice'. For most people (when I don't know their preference) I stick with either 'Happy Holidays' (which pisses off many people here in the good ole' south) or I really confuse them with a 'Live Long and Prosper'.

I guess if I really wanted to confuse them, I could spit out something in Gaelic (though I am very out of practice).

Lol, I'm feelin ya on that.. I've had to really reserve my "happy holidays" this year..the younger me would have probably been 60/40 the opposite way
I think it's safe to say it now till January, now that Santa is, wrapped up...

Nah. I just tell people the holiday that they celebrate. I don't like hurting anyone.

I give them a hearty Happy Festivus!

If I know someone's Christian, I say Merry Christmas. If not, Happy Holidays.

I say it cause I want to. Even at the food bank at a local church LOL. No spite here.

That's awesome. Thank you for sharing.

My wife had forbidden me to say "Frisky Festivus"

I say Happy Holidays.

Yes. I work in retail and have to deal with a lot of people who wish me a "Blessed Christmas." I retort "Good holidays to you." A few people will turn to me and glare as I go about my business. They already spent their money so they won't "not buy." I do it to maintain my own integrity knowing that there are some 30 winter holidays surrounding the winter solstice and Christians is but one.

Just to keep you abreast 'War On Xmas', I have been waging this war for about 5 years. It hasn't been pretty. Often, I will post a grinch or grumpy cat meme when the 'xmas' militia is least expecting it. It's guerrilla warfare. I've seen things. Shiver. Keep up the fight! (oh, and I don't look very xmassy, so I will get the passive aggressive 'merry xmas' upon occasion, but not so much anymore, and I fire back with either a Harry Fishnuts, or the simple 'happy holidays' depending on how the situation warrants)

I think I do hope that someone will get mad. Lol. Though I do mean it to be inclusive.
I’ve had a few say Merry Xmas back. And I laughed. Lol.

No, but I might start!