From canon law and the very nature of the Church as a visible society that is governed by authority.
Okay, you made it up then.
The problem is your confusion about occult heretics. An occult heretic is a hidden heretic, either kept in his heart or kept hidden by hypocrisy. It is NOT an open heretic who has yet to be brought to trial by ecclesiastical authority.
What is the rationale of admonishment from authority? Is it not only to correct the errant, but to manifest obstinancy in public as well? In in reality, you just made up the last part of your post. How do
you know that a heretic isn't "occult"? Where is
your line of demarcation? Public
knowledge is only half of the equation. Opposition to authority is as necessary to the equation than anything else. In fact, even if no other Catholic knew of the presence of a heretic and nevertheless was obstinate against authority, that man would then be considered a formal heretic and excommunicated as such. Thus the primary consideration is the relation to public authority. You are nullifying that to
your own confusion. Besides, who exactly are you refering to? We were making general statements about a diocese. Are you implying that we ought to sever the entire thing? Upon what grounds? The fact that you are disgusted that these criminals are still considered members of the Church. And round and round we go.