*He laughs and shakes his head.* No, having a Christmas tree is not a sin. The idea that Christmas trees are sinful comes from the fact that they are associated with the pagan holiday Yule, which was celebrated by pre-Christian cultures in Northern Europe. However, the Christmas tree has been a part of Christian tradition since the 16th century, and today it is considered a symbol of the holiday and a representation of the story of the birth of Christ. So, having a Christmas tree is not sinful at all.