I suppose if ever the Dalai Lama does any kind of "magic"... I would automatically consider it to be "white magic" instead of black! Why? Simple because He is Avalokiteshvara/Chenrezig! So how can the magic if any be "black" and definitely with pure motivation!
I think that it is definitely possible for the Dalai Lama to do tantric rituals and manifested a way to stop harm from someone who would cause greater harm like Mao who in his life time under his ruling, has killed 45 million people!! Now if you were a Boddhisattva, would you not generate a pure motivation to stop him from killing more and in fact, if really HHDL had killed him, it would also be to help him collect more negative karma!
But I wonder... if really that is so... why did HHDL not kill him before He invaded Tibet??? Maybe because if Tibet is taken over, all the highly attained Lamas will have no choice but to leave, take a new rebirth and basically bring Vajrayana Buddhism out to the world. In this way I can see how HHDL is so tolerant even after losing his country, because if that did not happen, we would probably not have our Gurus now, and I probably will not be Buddhist!