How could the Dalai Lama’s unlawful ban on Dorje Shugden practice possibly destroy Je Tsongkhapa’s tradition?

If the practice of Dorje Shugden is harmful then it follows that Je Phabongkhapa was not an authentic Buddhist master, and if he was not then there is no doubt that his heart disciples, Kyabje Ling Rinpoche and Kyabje Trijang Rinpoche (the Senior and Junior Tutors of HH the Dalai Lama) were also not authentic. These three Lamas are the most important Gelugpa Lamas of recent times. If these three are not pure Teachers then there is no doubt that the entire practice of the Gelug Tradition is invalid. This is the main issue that needs clarification. (Geshe Kelsang Gyatso, False Accusations Against the Innocent, Letter to the Editor of Newsweek, 05 May 1997)

[From Trijang Rinpoche, Spiritual Guide to both Geshe-la and the Dalai Lama:]

Furthermore, the definitive point of view, that these holy beings [previous incarnations of Dorje Shugden] were already fully enlightened innumerable ages ago, is clear if one examines the accounts of their lives, and if one were to say that a fully enlightened being could take birth as an ordinary gyalpo or tsen spirit, then one would be asserting that degeneration is possible from the state of full enlightenment or that someone could be both fully enlightened and an ordinary preta at the same time! Or else one would have to say that the accounts of those great beings’ lives are worthless. A mountain of absurd consequences, previously non-existent distorted ideas, would have to be accepted. (Trijang Rinpoche, Music Delighting the Ocean of Protectorsp. 9, circa 1967)