nolongersingle,
I do think there is a distinction between disputes between, say, MO and Yeshivish and between “meshichists” and the remainder of Orthodox Jewry. Most of the disagreements between the former are over matters of practice or outlook, for example, what to learn or not to learn, what to wear, how separate from secular society to be, etc. When you get down to the nitty gritty of ikkarei emunah, however, these groups fundamentally all agree, and that’s what makes us all Orthodox Jews. When a group begins to change one or more of these ikkarei emunah, however, we run into serious trouble. When Moshiach is declared to have come without any of the signs (ingathering of Jewish exiles, rebuilt Beis Hamikdash, knowledge of G-d fills the earth as water fills the seas, restoration of Malchus Dovid, resurrection, etc.), that represents a big change in one of our ikkarei emunah. We also have a history replete with examples of how dangerous this particular change is.
I personally don’t know enough about the meshichists themselves or the relevant halachos to say whether or not they are still within the boundaries of Torah Judaism, but I do know that the issues are quite different from the ones we typically debate in the CR.