I came across this quote from the Council of Constantinople regarding breaking communion with heretical Bishops:

“They who separate themselves from communion with their bishop on account of any heresy condemned by the Holy Synods of the Fathers, while he evidently proclaims the heresy publicly, and teaches it with brave front in Church - such persons, in excluding themselves from communion with their so-called bishop before Synodical cognizance, not only shall not be subject to canonical censure, but shall be deemed worthy, by the Orthodox, of becoming honor; for they condemn as teachers, not bishops but pseudo-bishops; and they do not cut up the unity of the Church by schism, but hasten to deliver her from schisms and divisions.”


Interesting...