Why do some who consider Christmas a sacred Christian holiday use pagan elements in their churches?

The biggest pagan element is a Christmas tree. I've personally seen evangelical and other churches who proclaim Christmas as sacred due to the symbolism of Jesus' birth, decry Wiccan's and other non-Christian faiths, yet have a pagan Christmas tree in their place of worship. I personally have nothing wrong with it, but just find it ironic. Are there other pagan symbols used in Christian churches you know of?