This article presents both the view of Dorje Shugden as a Buddha or Enlightened Being, as well as a spirit. So it is a balanced presentation. The view that he is enlightened is further elaborated on, to include his being an embodiment of Manjushri.
Furthermore Dorje Shugden, arose from Tulku Drakpa Gyeltsen, whom the fourth Panchen Lama, Lobzang Chokyi Gyeltsen ,had identified as the reincarnation of the 15th Gaden Tripa - Panchen Sonam Drakpa., who was himself a reincarnation of Duldzin Drakpa Gyeltsen, a close student of Lama Tsongkhapa. So with such 'credentials', how could Dorje Shugden be other than an Enlightened Protector?
Furthermore this website supports this article saying " The facts of this article are mostly accurate and so it paints a rather promising picture of acceptance of Dorje Shugden as an enlightened Protector, in the near future.
Thus Dorje Shugden could never have been a spirit, for if he were, how is it that the then 5th Dalai Lama, an emanation of Chenrezig, was not able to capture and destroy him?
Last but not least, if he were a spirit it is most unlikely that the two most influential Lamas of this age - Kyabje Pabongka Rinpoche and Kyabje Trijang Rinpoche - would work so vigorously and tirelessly to promote him and his practice for the benefit of all beings?