I think a lot of the D.L's outspoken rejection of Dorje Shugden is that it's been heavily intertwined with Tibetan nationalism, and his veneration as a deity isn't necessarily ancient. Given Tibet's tumultuous political past, I can understand why he wants to separate himself from any sect that can be seen as politically charged; but I do not think the Buddha himself would condone the banning of Dorje Shugden worshippers from dharma events, as His Holiness has done.

I fully agree that we should do investigating ourselves, rather than taking authority without question. Fire testing gold and all that.