Christianity spread under persecution for three centuries and then by state power for fourteen: Charlemagne, the Crusades, the Inquisition, the Americas. Isn’t comparing Islam’s first century with Christianity’s first three cherry-picking?

The comparison is limited to the founders’ generation on purpose, but the concern is fair: Christianity’s record after Constantine includes conquest and coercion, and that must be said with equal force. The narrow point is that Jesus and his first followers did not use force, whereas Muhammad and his immediate successors did, and that difference in the founders’ examples is what each tradition’s later coercers had to work with or against. Christians who used force violated their founder’s example. That is the claim, and it is as much a concession as a contrast.