--A proto-Protestant, Irenaeus wasn't.--
Another quote from Against Heresies:
Book 4, chapter 26
2. Wherefore it is incumbent to obey the presbyters who are in the Church -- those who, as I have shown, possess the succession from the apostles; those who, together with the succession of the episcopate, have received the certain gift of truth, according to the good pleasure of the Father. But [it is also incumbent] to hold in suspicion others who depart from the primitive succession, and assemble themselves together in any place whatsoever, [looking upon them] either as heretics of perverse minds, or as schismaries puffed up and self-pleasing, or again as hypocrites, acting thus for the sake of lucre and vainglory. For all these have fallen from the truth. And the heretics, indeed, who bring strange fire to the altar of God -- namely, strange doctrines -- shall be burned up by the fire from heaven, as were Nadab and Abiud. But such as rise up in opposition to the truth, and exhort others against the Church of God, [shall] remain among those in hell (apud inferos), being swallowed up by an earthquake, even as those who were with Chore, Dathan, and Abiron. But those who cleave asunder, and separate the unity of the Church, [shall] receive from God the same punishment as Jeroboam did.
That's a keeper!