The following is my commentary on the 11th point of The Anathemas of the Second Council of Constantinople (553 AD). This is not an endorsement of the SCoC, these are just some observations of mine.
If anyone does not anathematize Arius, Eunomius, Macedonius, Apollinaris, Nestorius, Eutyches and Origen, together with their impious, godless writings, and all the other heretics already condemned and anathematized by the holy catholic and apostolic Church, and by the aforementioned four Holy Synods and all those who have held and hold or who in their godlessness persist in holding to the end the same opinion as those heretics just mentioned; let him be anathema.
I think most in professing Christendom would consider their “two-deep anathemas” (i.e., two-persons deep) a radically eccentric & novel idiosyncrasy while very few would see it as simple child-like adherence to the biblical & apostolic teaching to abandon heresy and believe in Jesus (cf. Romans 1:16-17; Galatians 1:8-9; Philippians 3:8; 2 John 7 -11). I realize this doesn’t go over very well in modern Christendom or in academia, but it just might be the apostolic way (http://www.outsidethecamp.org/gospatone.htm and: http://www.outsidethecamp.org/gosprep.htm and: http://www.outsidethecamp.org/2John11.htm).
Seemingly the SCoC believed that the Person of Christ — His deity & humanity — was essential to the gospel (i.e., an essential gospel doctrine). Obviously they considered the denial of His Person to be a denial of the very gospel itself. That’s NOT to say they thought the Person of Christ was THE gospel since that would leave out other equally essential parts (e.g., the Work of Christ). [I just note in passing that the SCoC did not address the issue of ignorance of Christ’s Person but only the issue of knowing rejection.]
Picturing essential gospel doctrines as a Venn diagram we see that the SCoC considered the removal/denial of certain doctrines about Christ’s Person to be a removal/denial of the true gospel (Romans 1:16-17) and a replacement/affirmation of a false/anathematized gospel (cf. Galatians 1:8-9).
It should be clear that the SCoC’s “two-deep anathema” doctrine (cf. 2 John 9-11) cannot be the essential gospel doctrine since the “two-deep anathema” doctrine itself is based on the essential gospel doctrine (see: http://www.outsidethecamp.org/egd.htm).
The apostle John says that Christians are NOT to “speak a greeting” (i.e., χαίρω) to the person who does NOT bring “the doctrine of Christ.” The Greek word & context indicate that this “greeting” consists of significantly more than waving “Hi” with the hand or of raising up your chin while saying “Whattup?” to the heretic (cf. http://www.outsidethecamp.org/2John11.htm and: http://www.outsidethecamp.org/efl268.htm).
The SCoC’s essential gospel doctrine WAS the Person of Christ (presumably they were judging saved/lost by the essential standard of the gospel which they believed the Person of Christ was a necessary part). This explains why they would seek to emulate Paul by calling down the anathema on all who denied the doctrine of Christ’s Person (the “one-deep anathema”). They judged as unregenerate all those who did NOT confess orthodoxy regarding Christ’s Person (cf. John 8:24; Romans 1:1-4; 1 John 2:22-23, 4:1-3, 15).
The “two-deep anathema” was thrown down upon the heads of those judging by a different standard. The recipients of the “two-deep anathema” may have professed the (secondary? tertiary?) importance of Christ’s deity till they were blue in the face. Their “charitable judgment” of Arius not only revealed the “degree of importance” they placed upon Christ’s deity, it also revealed what “gospel” they actually believed to be the power of God to salvation to everyone believing.
Clearly the SCoC anathematized Arius (to pick one name from their list) because they saw his denial of Christ’s deity to be a confession of a false christ, a false god, and a false gospel (cf. 2 Corinthians 11:4; Galatians 1:8-9; John 8:24). They did NOT consider Arius a “very, very, muddled” Christian (cf. N.T. Wright/Marcus Borg); much less did they consider Arius an Apollos who “spoke and taught accurately the things of the Lord” but who nonetheless still required additional knowledge that he might speak of the Lord “more accurately” (cf. Acts 18:24-26).
They obviously didn’t consider the difference between their “Jesus” & Arius’ “Jesus” to be an issue of theological maturity or of “doctrinal perfectionism.” Arius wasn’t treated like one who just required gentle instruction and time to “grow in grace and knowledge” (2 Peter 3:18); as if knowledge of a mystical, amorphous, nebulous, or even a clearly-defined Arian christ had been “shone in [his heart]” as an immediate & inevitable fruit of regeneration rather than knowledge of the Jesus whom Paul preached (cf. 2 Cor 11:4). Arius also wasn’t treated like a true Christian who tenaciously & obstinately held to the heresy of believing in the false jesus of 2 Corinthians 11:4 who might (“at whatever pace and speed”) eventually “grow into” believing in the true Jesus of 2 Corinthians 11:3.
And lastly, they didn’t see their gospel & Arius’ gospel to be essentially the same KIND of gospel, differing mainly in DEGREES of understanding and clarity — as if the newly regenerated person began his Christian walk believing the false gospel of Galatians 1:8-9 and then later “grew into” (cf. 2 Peter 3:18) believing the true gospel of Romans 1:16-17, all the while believing he was regenerate while believing the false gospel of Galatians 1:8-9 (cf. Phil 3:8).