"But a Christmas Tree is secular"
A Christmas Tree is a Pagan symbol which was adopted by Christians for their Christmas holiday.
It's not a "Secular" symbol, it's a symbol which Christians adopted for their holiday.
1) If it's secular, how come everyone calls it a Christmas Tree, and Christians get upset when it's called a "holiday tree?"
2) What is it's "Secular" meaning?
You are correct The Christmas Tree is derived from a Pagan holiday just as the Easter Bunny is and Halloween.
Since most Christmas Trees are actually Scotch Pines or Douglas Fir's I would say they are *Trees* and they are celebrated at christmas time signifying the season of gift buying and decorations. My point is a Christmas Tree does not signify anything in Christianity unless Jesus was really born under a Scotch Pine and not in a manger.