I don't say it's not possible; anyone can call themselves anything they like. However, from the perspective of Christianity, it is not acceptable to follow the path of the God/Goddess. There is only one God in Christianity. Many Christians (Roman Catholics in particular) get around it by revering Mary, Mother of Jesus. It's quite possible to be a pagan and adhere to the teachings of Jesus.
You may be referring to my statement that it's not possible to be both Wiccan and Christian. The two are separate faiths and there are too many differences for them ever to work together. It would be like trying to play for two different football teams. For example, Christianity holds the devil up as the ultimate evil; Wiccan worship the Horned God who looks exactly like the Christian devil. Wiccans practice such things as fertility magic; Christians would be horrified at the idea. So while you might uphold the principles of Christianity but practice Wicca, you can never really be both.