Daasyochid, klal yisroel has a chezkas kashrus and kol deparush meruba parush.
Chabad is kavua. Plus the rebbe’s “rebbe = Hashem” atzmus sicha is a reyusa on every member of Chabad.
Daasyochid, I will say that their usual excuse is “those aren’t the regular Lubavitchers, just the crazies”. They don’t use the term apikorsim because they refuse to acknowledge the elephant in the room.
But for us, we are trying to be mekareiv them, let’s use the appropriate term.
I can’t speak for Rav Menashe Klein zt”l. But I accept his pask as someone who knows the bounds of appropriate and inappropriate chassidus.