So, maybe this claim is to divert people's attention from his promise to obtain Tibet's independence in a stipulated time of which he failed to get.
Om Mani Padme Hung!
Yes, I agree Galen. I have always wondered about the timing of the Dalai Lama ban on Dorje Shugden. There were no spiritual unrest or quarrels amongst the Tibetan Buddhist community that might have prompted the two most aggressive attacks on Dorje Shugden in 1996 and 2008 and therefore the Shugden affair does not seem to have its roots in any spiritual matter at all.
There were however, 2 politically related incidents that could explain why a red herring was needed in 1996 and 2008. A few years prior, in 1988 the Dalai Lama had unilaterally given up the pursuit of Tibet's independence, opting instead for an autonomous Tibet under the sovereignty of China. This would have been a terrible blow to the Tibetans had it been made very public but it was not and soon, in 1989 the Dalai Lama was awarded the Nobel Peace Prize and with that all Tibetans basked in the glory of their spiritual and temporal leader, thinking that finally Tibetan independence was within grasp. But by 1995, when it became clear that Tibetans were not even close to returning to their homeland, rumblings of Tibetan independence started again and this time spearheaded by the Dalai Lama's own brother. The public split between the Dalai Lama and his own brother was not good press for the Dalai Lama and attention was being drawn towards Tibet's independence versus autonomy. The louder the call for Tibet's independence, the more it was becoming evident that Tibet's own leader had hawked off what all Tibetans treasured.
And so the Dalai Lama had to produce a false witness in Nechung (remember Nechung bows to the Dalai Lama) claiming that Dorje Shugden was the cause of the failure in Tibet regaining its independence. And in addition the Dalai Lama added to the stake another thing all Tibetans treasure - that is the Dalai Lama himself. The Dalai Lama claimed that the practice of Dorje Shugden shortens his life knowing full well how he is revered and loved by Tibetans as their god-king.
That worked and attention shifted to a deity that had been propitiated for hundreds of years and Tibetans turned on their own kind in retribution.
The call for Tibet's independence cooled off somewhat until the years leading into the Beijing Olympics and attention again focused on the China-Tibet issue. As Tibetan independence movements geared up for action (perhaps even under the instigation of the Dalai Lama's own office as China has claimed) the call for Tibet's independence became louder and all this nationalistic fervor can only serve to highlight that it was the Dalai Lama himself who gave away the nation's independence in Strasbourg years back. And so, there was a need to create a bigger distraction to divert attention away from the Dalai Lama's failure and this time the Dalai Lama went for the jugular with the Shugden practicing monks and lay people.
And why Dorje Shugden was made the culprit? It would not have been expedient to pick on the State Oracle as much of the political decisions were made in consultation with Nechung and if Nechung had been wrong all these time, it would also mean that the Dalai Lama has also been wrong. Neither could the Dalai Lama ban a practice outside his own Gelugpa sect. None of the other sects regard the Dalai Lama as their spiritual head and therefore it had to be Dorje Shugden.
Not that the Dalai Lama himself believes it and His Holiness let the cat out of the bag a few times stating confidently that he can look forward to a long time. The Dalai Lama may be in collusion with Dorje Shugden to spread the Dharma with the added play by Nechug. Or it could just be that the Dalai Lama picked on Dorje Shugden knowing fully well that Dorje Shugden is a fully enlightened Buddha and will always upkeep the Lojong rule and let the other party have the victory.