As rancorous as it seems, the role that religion plays in American politics and everyday life today is a far cry from the role it played in the 5th century. Today we wrangle about the application of belief systems, in those days they fought about the very meaning of the belief system and the ramifications it had in everyday life. Then, more so than now, God was everywhere, not just in indignant people and talking heads; God permeated the air and was thought to be vital to life and therefore to politics.
When the bishop of Constantinople (i.e. the Pope in the East) muddied the waters about the nature of Christ it would be as if Pope Francis declared that most of the teachings of the Church were wrong. When doctrine is not well defined, though believed, it can be the cause of scandal among the faithful. Blind acceptance is not the problem but taking truths for granted is. The little understood or misunderstood truth can be fodder for error and those not well taught can easily be misled or fall into error.
Cyril fought hard but he did so with love as the end goal. After the bloody and cruel fight he was the first to seek reconciliation in order to bring all together under Jesus, understood as both God and human, and into the protection of his mother the Theotokos.
Today we might learn a lesson about extracting the truth from human foible and living to make it vital and important in the everyday, not just on passing, knee-jerk, hot-button issues. Today many of the arguments remain the same, as do the errors which lead the faithful astray, only the proponents have changed.

P.S. This is not about everyday relativism, this is about foundational truths.

Forgive me for having resolved to speak not only against a king, but also for the glory of Christ, the great King, who reigns with his Father over the world; it is with him alone that it is true to say: "Through me kings reign", because he is the "Lord of glory" in heaven and on earth. It is because of that the champions of the divine teachings (us, in fact - given this office by Christ) must oppose those who intend to defile his glory and to plead his cause, to appear sound to readers, to be a more useful aid for those whose heart is easily led astray and is inclined to yield to difficulties, and for those on the other hand who are well established in the faith to be a kind of stick able to support them in the strengthening of this faith and to maintain undimmed the tradition of orthodoxy.
Who is it that has entered into war against the glory of Christ? They are legion, those who at various periods have let themselves go at this foolishness, driven by the perversity of the devil; but none as went far as Julian, who damaged the prestige of the Empire by refusing to recognize Christ, dispenser of royalty and power. Before his accession to the throne, he was counted among the believers: he had even been admitted to Holy Baptism and had studied the Holy Scriptures.
But some sinister characters, followers of superstition, entered, I do not know how, into connections with him and sowed in him the maxims of apostasy; then, allied with Satan in this design, they led him towards the practices of the Greeks and transformed into a servant of impure demons one who had been raised in holy churches and monasteries: "bad company corrupts good upbringing", as the very wise Paul says. However, I affirm that those who wish to preserve solid thought, and who keep in their spirit, like an invaluable pearl, the tradition of the true faith, do not have to offer to the peddlers of superstition any occasion to insinuate themselves, yet in any case should speak to them freely. Is it not written: "You will be holy with the holy, irreproachable with the irreproachable, chosen with the chosen, and you will outwit the cheat"? With the eloquence with which he was gifted, the all-powerful Julian argued against our common Savior Christ; he composed three books against the holy gospels and against the very pure Christian religion, he used them to shake many spirits and to cause them uncommon wrongs. Indeed, the light-minded and easily seduced fall easily into his sights, and constitute a welcome amusement for the demonic powers; but not the spirits of those strengthened in the faith which do not let themselves be disturbed yet sometimes they believe that Julian knows the holy and divine Scriptures, since he uses them in his own works — without otherwise knowing well what it says!... — a number of testimonies that he borrows from them.
Very many followers of superstition, when they meet Christians, overpower them with any kind of sarcastic remarks, and rely on the works of Julian to attack us, which they proclaim to be of an incomparable effectiveness, adding that there never was a learned man on our side able to refute them, or even show them at fault; also, at the instigation of more than one person, and full of confidence once again in the word of God: "Get under way, and I will open your mouth!", I put myself to the duty of rebutting this Greek eyebrow raised against the glory of Christ, to help to the extent of my abilities those which have been deceived, in order to convict of error and of ignorance of the Scriptures the man who has accused our common Savior Christ.

-- Against Julian, Prefatory Address (3-5)

For in no other way could we have learned the things of God, unless our Master, existing as the Word, had become man. For no other being had the power of revealing to us the things of the Father, except His own proper Word. For what other person "knew the mind of the Lord," or who else "has become His counselor? " Again, we could have learned in no other way than by seeing our Teacher, and hearing His voice with our own ears, that, having become imitators of His works as well as doers of His words, we may have communion with Him, receiving increase from the perfect One, and from Him who is prior to all creation. We who were but lately created by the only best and good Being, by Him also who has the gift of immortality, having been formed after His likeness (predestined, according to the prescience of the Father, that we, who had as yet no existence, might come into being), and made the first-fruits of creation have received, in the times known beforehand, [the blessings of salvation] according to the ministration of the Word, who is perfect in all things, as the mighty Word, and very man, who, redeeming us by His own blood in a manner consonant to reason, gave Himself as a redemption for those who had been led into captivity.

-- Against Heresies, Book V, 1

We call this feast "Peter AND Paul", which is in juxtaposition to the "Peter OR Paul" or "Peter VS. Paul" thinking that often goes on.
Though there may have been some amount of it at the time, we see now that theirs is not a rivalry but a complementary relationship. Many of our brothers and sisters in Christ, throughout time, have tried to emphasis one over the other, or to surpass one with the other in order to explain some point or to justify/deny some belief system or tradition. But regardless of how they lived and ministered, they died in sync in Rome. One a citizen, the other a Jew. One martyred 'nobly' the other ignobly but in the end, both martyred for Christ.
So it is Peter AND Paul, as apostles of Jesus, that we celebrate; they who did Christ's bidding, not for their own gain but for his. Neither surpasses the other in preaching or theology and most importantly, neither surpasses Christ. We celebrate them together like so many of the early Roman martyrs (tomorrow for example).
I think that is what so many people miss. We do not "follow Paul or Apollos" (cf. 1 Corinthians), we follow Jesus with their help and guidance. It is his mandates and path, not Peter's or Paul's that we follow. So many problems between denominations would be solved if we just walked that line.

It is truly right and just, our duty and our salvation,
always and everywhere to give you thanks,
Lord, holy Father, almighty and eternal God.
For by your providence
the blessed Apostles Peter and Paul bring us joy:
Peter, foremost in confessing the faith,
Paul, its outstanding preacher,
Peter, who established the early Church from the remnant of Israel,
Paul, master and teacher of the Gentiles that you call.
And so, each in a different way
gathered together the one family of Christ;
and revered together throughout the world,
they share one Martyr’s crown.
And therefore, with all the Angels and Saints,
we praise you, as without end we acclaim:
Holy, Holy, Holy Lord God of hosts...

-- Preface from the Solemnity of Peter and Paul

We are not a new philosophy but a divine revelation. That's why you can't just exterminate us; the more you kill the more we are. The blood of the martyrs is the seed of the church. You praise those who endured pain and death - so long as they aren't Christians! Your cruelties merely prove our innocence of the crimes you charge against us. When you chose recently to hand a Christian girl over to a brothel-keeper rather than to the lions, you showed you knew we counted chastity dearer than life. And you frustrate your purpose. Because those who see us die, wonder why we do, for we die like the men you revere, not like slaves or criminals. And when they find out, they join us.

-- Tertullian, From Apologeticum