The point is not about comparing Dorje Shugden to Mara. Certainly that is not correct and I believe Dharmaspace do not mean that. He is just using logic about what is illogical. Hence, Dorje Shugden is a Buddha.
First of all, the source of this article is the "Yellow Book". Whether we want to regard it as a reliable source is by itself a debate. But lets just for argument sake take these incidents as true, then we can make a few deductive conclusions:
1) The Panchen Lamas who died young because the karma of beings at that time. It is well known that many lamas will chose take another rebirth if he feels it is better to do that; for various reasons too many to discuss here all but I will give a few examples. By doing that these lamas have the intention to teach a final lesson to the beings/disciples he left behind and to those who life he chose to be reborn into. If could be in a different place with totally different people around him. In the case of the Panchen Lama; since he has to be reborn as the next Panchen Lama, the environment and people surrounding him most likely will be similar, the the conclusion would most likely that he was purifying the karma of beings of that time.
2) Since the Panchen Lama is Amitabha, he can never be hurt. So by manifesting sickness and others obscurations; it is part of a great play that is yet to fully played out; I feel. To me even the spiritual tutor of the Panchen Rinpoche at that time, Yongzin Kachen Ang Nyima is part of that play.
3) The karma of beings in this degenerate age is so ...well degenerate that it needs the Buddhas skillful means, over a few hundred years in a great play on the stage of samsara to benefit the the optimum numbers of beings via the practice of the protector of this degenerate age, the Lord, King of Dharma Dorje Shugden, who the 4 great Drakpas himself, who is none other then Lord Tsonkhapa and Buddha Majushri. This is unmistaken.
It is all because of our karma. All the play of the ban and everything. This is why the Buddhas call this the degenerate age. For those fortunate enough, Dorje Shugden practice is at our doorstep.