AesopFan:

Which was the important point of my comment, I thought, though you clipped that part off when quoting me.

Yes, I know Christianity was never One Big Happy Family. You didn’t even touch on how the Gnostic Christians were treated.

And later, the persecutions and inquisitions became horrific. No excuses IMO.
Nonetheless, I would still argue that this is the default of Christians set by Jesus:
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By this shall all men know that ye are my disciples, if ye have love one to another.

–John 13:35 [KJV]
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Muhammad never said anything like that.

I admit there were some rough patches, but Christians didn’t start off killing each other, and after they started, they did stop.

Muslims have never ceased their efforts to subjugate the world and anyone who disagrees with their notion of what Allah wants, including other Muslims, which has always included killing people.

Actually, they did.

Read Acts and Paul’s letters (I just finished a good commentary on them).

The conversions of gentiles began within the first decade after Christ’s resurrection and ascension and led to the first, somewhat trivial, controversy between Jewish and mostly-Greek individuals, although not resulting in a leadership split or challenge: the Apostles were the acknowledged authorities and settled the matter satisfactorily (providing welfare to widows fairly, Acts 6:1–7).

The next “factions” developed after Paul and other missionaries successfully proselyted to the gentiles outside of Judea, between the Judaizers (who said that all gentile converts have to follow Mosaic Laws in their entirety, or at least circumcision and a few others) and the “Gentilists” (my term) who won a compromise from the leaders in Jerusalem (James, Peter and the other apostles) on just four qualifications related to Jewish ritual and ethics. Again, the controversy was settled because of the unity on Apostolic authority.
*
Acts 15:28 For it has seemed good to the Holy Spirit and to us to impose on you no further burden than these essentials: 29 that you abstain from what has been sacrificed to idols and from blood and from what is strangled and from fornication. If you keep yourselves from these, you will do well. Farewell.
*
Next were the various “personality congregations” who asserted that they would only follow the person who baptized them, not necessarily the leaders in Jerusalem or their official representatives to the gentile churches (Paul, Barnabas, and a few others). Paul had to assert their delegated authority from the Jerusalem apostles (and as an apostle himself) to tamp down nascent schisms.
1 Corinthians 3:4-9 New King James Version
4 For when one says, “I am of Paul,” and another, “I am of Apollos,” are you not carnal?…

Then Paul warned against newly-rising self-appointed leaders in the Christian churches who brought in heretical doctrines contrary to those taught by Paul (and his immediate companions) and Peter (and the Judea-centered leaders).
Acts 20:29 For I know this, that after my departing shall grievous wolves enter in among you, not sparing the flock. 30 Also of your own selves shall men arise, speaking perverse things, to draw away disciples after them. 31 Therefore watch, and remember, that by the space of three years I ceased not to warn every one night and day with tears.

Fortunately, the killing held off for a few hundred years, but still predates the events Gringo noted (“Think Catholics and Protestants in 17th century Europe”) .

All accusations of heresy, however much they might be doctrinally motivated, eventually become rival factions vying for leadership, and they didn’t always limit themselves to just “cancelling” their opponents in the current fashion. However, for nearly a thousand years, the executions of heretics was done by the state, not the Church per se.

https://christianity.stackexchange.com/questions/19368/who-was-the-first-church-father-to-argue-for-executing-heretics

Technically, the first ecclesiastical authority to say that heretics should be persecuted was Pope Gregory IX in 1229. The first Church Father to say that heretics should be compelled to recant would be Augustine around 400 AD.

The first heretic actually put to death (385AD) was killed by the Emperor – and the Pope was very annoyed at the development. It wasn’t for another 800 years that the church followed suit.

That said…

The church typically did not execute heretics. Rather, the state, sometimes at the behest of the church or other times of a monarch desiring no discord amongst his subjects, would carry out such persecution and executions.

The earliest Christian heretics were not put to death by the Church, but rather by the Roman Empire. Note for example, the first “heretic” to be executed – Priscillian – was put to death not by the church, but rather the state. Furthermore, those responsible for getting the state to put him to death were subsequently excommunicated by the Pope for their actions.

Per this article:

The first person to define what heresy was Irenaeus, Bishop of Lyons (2nd Century). He simply warned about the dangers of a multitude of opinions on how God works.

The first person to make heresy a crime was Emperor Constantine (320s). He made the assembling of heretics an offense, the penalty of which was the confiscation of property.

In 380 AD under the Christian Emperor Theodosius I laid down the rule that only the Catholic Christians could define orthodoxy within the confines of the Roman Empire. As noted already, it was under his reign that the first heretic was put to death.

Augustine (AD 354-430) taught that error has no rights. He cited biblical texts, notably Luke 14:16-23, to justify the use of compulsion

Emperor Justinian issued severe laws against heretics in AD 527 and 528. (It should be noted, this was in the aftermath of a severe series of riots that left thousands dead.)

Pope Paschal II (Pope from 1099 and 1118) was the first to say that anyone who disagreed with the apostolic see was a heretic.

Pope Innocent III (1199) was the first to declare heresy to be high treason against God, having already called for the execution of those who persisted in their heresies after being excommunicated.

It was not until 1229 that Pope Gregory IX declared that it is the duty of every Catholic to persecute heretics.

Which they did.
https://en.wikipedia.org/wiki/List_of_people_burned_as_heretics
(or at least some we know about, beginning in 1076)

Citations to post-Reformation examples of persecution and killing up through the 19th century, such as in LDS history including the infamous Missouri Extermination Order, are easily available on the internet.

Still, there does not seem to be an analogous Sunni-Shia split in the annals of Christendom, where essentially a single dividing line of contested succession has existed since the beginning and still drives animosity and violence.

In “The Lord of the Rings”, Gandalf (I think) said something like “The victor in the battle between our enemies will emerge stronger than either alone.”

When “Biden”, in “his” extraordinary wisdom, hearts Iran (& Co.) with billions upon billions upon billions of dollars, ISIS understands EXACTLY what that means. (So does Saudia Arabia, by the way. And the Emirates. And Egypt, etc., but they don’t have the same—let’s call it—“freedom of movement” that ISIS has.)

Yes, ISIS gets the message, loud and clear.

Not American liberals, though, whose cluelessness is elevated, in their own eyes, to sheer brilliance (to be sure,”Biden”‘s O-SO-SUCCESSFUL campaign of demonizing “his” political opponents plays a HYUGE role in this cluelessness—heck, if Trump is a NAZI, then ANYTHING is possible…and justifiable!! Yes, it is, even unto destroying the good ole U. S. of A., not that they’d actually see it as “destruction”, of course—they can’t: they’re totally blind to it. Their “shields are totally down and broken).

So when ISIS just happens to notice that “Biden” is helping the mullahs create a Neo-Fertile-Crescent (an Arch of Shi’ism) across the Middle East and down into the Arabian Peninsula, ISIS understands exactly what that means.

Not American liberals, though (who would appear to to twist themselves into knots to believe it means that “Biden” is still a firm supporter of Israel(!)).

But for ISIS, this has NOTHING to do with Israel.

This has everything to do with the American decision (as ISIS sees it) to continue to work to destroy the Sunni nations (let’s call it GWB vs. Saddam Hussein, THE SEQUEL).

And ISIS, very sensitive about movies like this, does not like it one bit, no it does not! No popcorn for ISIS…or rather, for them, there’s far better things than popcorn…

(Not to worry, though. They’ll take care of Israel later.)