http://www.fisheaters.com/customschristmas1.html
I particularly like how this article puts it:
"Today the Christmas tree can be the symbol of the peace that Jesus brought, that must be re-established between God and human beings. Because it is evergreen, it is the symbol of that immortality which Jesus said he possessed and would bring to us: "I am the life; those who believe in me even if they die will live". The tree lit by little lights is the symbol of the light that Jesus brought to the world with his birth: "He was the light that shines in the darkness... and enlightens every man..." (cf. Jn 1:4-14). And finally, the fir tree, with its tip pointing to heaven, indicates God's presence to us and the place where we are all awaited.
All this endows the Christmas tree, in harmony with the crib, with the religious and Christian significance of salvation that the Son of God brought to the whole world by his humble birth"
https://www.catholicculture.org/culture/library/view.cfm?recnum=6304
http://www.catholicculture.org/news/features/index.cfm?recnum=34135
I find that you're being a bit hypocritical in that you seem to be saying that pre-Christian cultures somehow have an exclusive claim to using trees in religious and/or seasonal celebrations. No one has exclusive claims to things like trees or other things used as symbols.
I'm not claiming Christmas has priority claim to all, but it does to me as a Christian. You, and everyone else, can celebrate what you wish. Or not celebrate anything. I really don't care what society at large does because it has no impact on me that I don't allow it to have.