The Barbarity of Christianity (as compared to Islam)

We don't have much information about the first few centuries of Christianity

It may very well be a moot point if the deity is omnipotent and doesn't much care what crashfrog thinks, but that is another discussion.

For the first three centuries Christianity was placed in the most unfavorable circumstances, that it might display its moral power, and gain its victory over the world by spiritual weapons alone. Until the reign of Constantine it had not even a legal existence in the Roman empire, but was first ignored as a Jewish sect, then slandered, proscribed, and persecuted, as a treasonable innovation, and the adoption of it made punishable with confiscation and death. Besides, it offered not the slightest favor, as Mohammedanism afterwards did, to the corrupt inclinations of the heart, but against the current ideas of Jews and heathen it so presented its inexorable demand of repentance and conversion, renunciation of self and the world, that more, according to Tertullian, were kept out of the new sect by love of pleasure than by love of life. The Jewish origin of Christianity also, and the poverty and obscurity of a majority of its professors particularly offended the pride of the Greeks, and Romans. Celsus, exaggerating this fact, and ignoring the many exceptions, scoffingly remarked, that "weavers, cobblers, and fullers, the most illiterate persons" preached the "irrational faith," and knew how to commend it especially "to women and children."But in spite of these extraordinary difficulties Christianity made a progress which furnished striking evidence of its divine origin and adaptation to the deeper wants of man, and was employed as such by Irenaeus, Justin, Tertullian, and other fathers of that day. Nay, the very hindrances became, in the hands of Providence, means of promotion. Persecution led to martyrdom, and martyrdom had not terrors alone, but also attractions, and stimulated the noblest and most unselfish form of ambition. Every genuine martyr was a living proof of the truth and holiness of the Christian religion. Tertullian could exclaim to the heathen: "All your ingenious cruelties can accomplish nothing; they are only a lure to this sect. Our number increases the more you destroy us. The blood of the Christians is their seed." The moral earnestness of the Christians contrasted powerfully with the prevailing corruption of the age, and while it repelled the frivolous and voluptuous, it could not fail to impress most strongly the deepest and noblest minds.

It also doesn't address how Christiantiy became later, and how it's exclusive nature allowed for cruelty and barbarity against non-believers.

It was only when Christianity became the power that it had the capability to be a problem.

Unlike Mohammed, Jesus or his apostles and adherants never harmed anyone physically.

Or crashfrog might say that simply that God's behavior clashes with his moral framework, and therefore according to that framework God is immoral. Crashfrog might also say that his moral framework is just a valid as God's; indeed, in a fit of arrogance usually exhibited by deities and their followers, crashfrog might even say that it is his moral framework that is absolute and that it is God, omnipotent he may be, who is wrong and unjust.

Anyone can point at themselves with equal validity. God's personal choice of morality is no less arbitrary than anyone else's