https://ecauldron.com/forum/holidays-and-festivals/christmas-wasn't-stolen-from-the-pagans/?PHPSESSID=f81k0dnt9ianr9p6qan5qbng5a

+++The pagans of northern Europe celebrated (and continue to celebrate) Yule at that time, long before Jesus was born and most of present-day Christmas customs, including carols, Christmas tree etc. have, beyond any doubt, origins in Celtic or Germanic winter solstice customs.+++

Here again we have a "yes, but." You've failed to provide an important connecting point: Did Christians have contact with northern Europeans at the time of the setting of the date for Christmas? In fact, no. Christmas was set near the date of Yule before Christians were evangelizing northern Europeans or, according to extant evidence, had any meaningful contact with that culture. (And again, you've failed to provide support for the assertion that coincidence in time equals shared origins.)

Furthermore, the "present-day Christmas customs" you cite are NOT universal Christmas customs by any stretch of the imagination. They are NORTHERN EUROPEAN Christmas customs. Christianity has always engaged in what's called "inculturation" in theological jargon - the acceptance of aspects of local culture into church customs. For example, in Hawai'i, hula is used in church celebrations because of its importance in local culture.

Others can talk about carols better, but carols-qua-carols didn't appear until the middle ages, so I'm not really sure how you're claiming Northern European pagans fit into that. Many Christian hymns are set to older tunes, but again, that was common cultural custom. And most of the tunes are medieval themselves.

As for trees, I have a terrifically boring revelation for you: Since the second century, churches (formal separate buildings or informal house churches) were "required" (in quotes because the authority structure was quite informal until the 10th century or so) to have green plants in the church as an expression of creation and new life. For all services, not just special ones. You can go into any Catholic Church today for a service and there will always be plants except on Good Friday. (And if not, they ought to be reported to the bishop; it's liturgical law and they're breaking it.)

If you're in Northern Europe, and it's late December, and you're required to have greenery in your church, what are you going to use?

Oh, right - fir trees, evergreen boughs, and holly.

Which is probably, more or less, the same theological justification for their use in pagan winter celebrations.

The reason Christmas trees are so popular as a symbol of the season is because Hallmark is a company coming out of a Northern European-derived culture that maintains those Christmas traditions. Prior to 1950, Italians would have looked at you like you had two heads if you tried to give them Christmas trees. (Well, there are evergreens in Italy too and some were used as Christmas decor, but not exclusively because there's other greenery available during that season, so there's not the same strong association of Christmas with firs. Lots of cultures prefer Christmas lilies. In Northern Europe, lilies had to be confined to Easter.)

(http://www.autoadmit.com/thread.php?thread_id=4994434&forum_id=2#43682634)