Whatsaktome – really? You really think it’s possible? Out of all the potential moshiachs – Dovid hamelech, Daniel, Chazal, Rabi Shimon Bar Yochai, etc etc, the biggest of all of them is the Rebbe? That’s insane. That’s why any Chabadnik who believes that the Rebbe “could” be Moshiach has something wrong in his yiddishkeit – because he implicitly believes (whether he is aware of it or not) that the Rebbe is bigger than all the other gedolim who are also dead.
Now it’s possible that while the Rebbe was alive he was the biggest in his generation – and even a potential Moshiach. That’s not nuts at all to believe in. But once he starts competing with dead people, no way he’s the greatest.