Pretty good post. I think early father or Didache says not to schism but to pacify those that contend, like both sides have a responsibility as you seem to allude to…
"Do not long for division, but rather bring those who contend to peace. " (Didache ch. 4)
I am not sure this pertains to doctrinal schism, which is clearly denounced in the NT.
1 Cor 12:24-25
But God has so composed the body, giving more abundant honor to that member which lacked, that **there should be no division **(Gr. and AV schisma) in the body, but that the members should have the same care for one another.”
1 Cor 1:10-13
“Now I exhort you, brethren, by the name of our Lord Jesus Christ, that you all agree, and there be no divisions (Gr. schisma) among you, but you be made complete in the same mind and in the same judgment. For I have been informed concerning you, my brethren, by Chloe’s people, that there are quarrels among you. Now I mean this, that each one of you is saying, I am of Paul, and I of Apollos, and I of Cephas, and I of Christ. Has Christ been divided? Paul was not crucified for you, was he? Or were you baptized in the name of Paul?” (denominational Protestantism!)
1 Cor 11:17-19
“But in giving this instruction, I do not praise you, because you come together not for the better but for the worse. For, in the first place, when you come together as a church, I hear that divisions exist among you; and in part, I believe it. For there must also be factions among you, in order that those who are approved may have become evident among you.”
1 Tim 1:3-4
3 As I urged you when I was going to Macedonia, remain at Ephesus that you may charge certain persons
not to teach any different doctrine,
The modern term “doctrinal distinctives” that is used to justify the fact that there are so many contradicting doctrines is not at all supported in the early Church.
Eph 4:3-6
eager to maintain the unity of the Spirit in the bond of peace. 4 There is one body and one Spirit, just as you were called to the one hope that belongs to your call, 5** one Lord, one faith, one baptism, **6 one God and Father of us all,
Rom 16:17 (Douay Rheims)
17 Now I beseech you, brethren, to mark them who make dissensions and offences contrary to the doctrine which you have learned, and avoid them.
The reason that Catholics cannot accept or make concessions to Reformation doctrines is because they are contrary to the doctrines that were handed down to us through the paradosis. They are a significant departure from the Apostolic faith -
And Ignatius:
Ignatius (died c. 106 ad) writes to the Philadelphians:
CHAP. III.–AVOID SCHISMATICS: “Keep yourselves from those evil plants which Jesus Christ does not tend, because they are not the planting of the Father. Not that I have found any division among you, but exceeding purity. For as many as are of God and of Jesus Christ are also with the bishop. And as many as shall, in the exercise of repentance, return into the unity of the Church, these, too, shall belong to God, that they may live according to Jesus Christ. Do not err, my brethren. If any man follows him that makes a schism in the Church, he shall not inherit the kingdom of God. If any one walks according to a strange opinion, he agrees not with the passion [of Christ].
“Keep yourselves, then, from those evil plants which Jesus Christ does not tend, nor that wild beast, the destroyer of men, because they are not the planting of the Father, but the seed of the wicked one. Not that I have found any division among you do I write these things; but I arm you beforehand, as the children of God. For as many as are of Christ are also with the bishop; but as many as fall away from him, and embrace communion with the accursed, these shall be cut off along with them. Take ye heed, then, to have but one Eucharist. For there is one flesh of our Lord Jesus Christ, and one cup to show forth the unity of His blood; one altar; as there is one bishop, along with the presbytery and deacons, my fellow-servants: that so, whatsoever ye do, ye may do it according to [the will of] God.”