I have to say (being a huge Rossi fan) that this action was not correct or fair at all. Everything else than a disqualification of Rossi would be huge surprise. One can clearly see how Rossi takes three good looks at MM before he moves his left leg against (I'm not quite sure) MM's shoulder or even helmet that causes him to crash. That's not fair sportsmanship!
BUT, as Ben Spies just said, MM asked for it twice, in PI and Sepang again. It is more than obvious that MM just lets JL pass, not even trying to battle him and just waits for Rossi to close up. Then he does several risky and very hard moves on Rossi. I think they touched more then once before the final crash.
I have no idea about MM's intention behind all these actions, but I can undertsand Rossi getting angry at MM and showing this reaction (which doesn't make this action legitimate!). As for MM, you either pass and disappear or you let Rossi pass and try to follow his pace. That's why Rossi waived at MM before the incident "come and follow me to close on JL". Everything else in such an early stage of the race does just not make sense for a race strategy in my oppinion.
We'll see what the reace direction will decide. But I think that Rossi's championship sadly was lost the moment he crashed with MM.