If other religions used the tree in their holidays, then I could see that.
But this is exactly like calling a Menorah a “Holiday Candle”. It’s a Jewish symbol. There is no-one to offend here.
Christmas Trees are used in the celebration of Christmas. Not any other holiday.
Conifers are cut down and decorated for Christmas and only Christmas. If anybody knows of another so celebrated holiday, let us know. There is possibility that I am unaware of one. And is it in December?
Let’s call it a Spiritual Tree or Spiritual Candle so no one can be offended!