In chapter 11 of Hilchos Melachim in the Frenkel, uncensored, edition of Mishneh Torah, the Rambam writes that the reason Hashem allowed the events of Y Hanotzri (and Mohammed) to take place were to spread the belief in Mashiach, even though it was a totally false belief. Then when the real Mashiach comes he will be accepted by all who will forsake their incorrect beliefs.
So even though the belief that the Lubavicher rebbe was/is Mashiach is totally false, I suppose there may be some good that will eventually come out of it.
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