“In my experience with Chabad (and I have quite a bit), the Messianist movement is overblown by a lot of outside people.’
Please prove me wrong. See if you can get any Lubavitcher to say unequivocally that the rebbe is not Moshiach.
The vast majority of Rabbonim and Roshe Yeshiva and Poskim cannot be lying to us. And yes, it is k’fira and apikorsis to believe that a dead man can be Moshiach.
And don’t lecture about loshon hara; see the viciousness of Crown Heights toward Reb Ahron Kotler zt’l, Rav Shach zt’l, the Satmer chassidim, and many others.
Do not mistake a Lubavitch rest stop as a hechsher for their dangerous Moshiach pronouncements.