Furthermore, Christianity was adopted by a Roman Emperor, but in the same years Islam was busy conquering territory for the ol' Arabian moon god, Christianity was not spreading itself with the sword. Later, after the Crusades, with the Teutonic knights and with the Spanish in America, perhaps, but basically, Christianity has spread with missonaries preaching, not soldiers putting the sword to people and telling them convert or die, as does Islam.
You're a number of centuries off between the adoption of Christianity by Constantine and the dealings of Muhammed. Secondly, you need not go to the middle ages to find the spread of Christianity by the sword. You need only look at Charlemagne.
I am in no way trying to defend Islam, either in its initial spread or in its present attempts to conquer by means of the unthinking brutality of suicide. I feel that much of the Islam clergy would be more appropriate in the Stone Age. However, the topic of this post was how brutal Islam was in the past. My point is that, during that era, Christianity was just as violent.
The difference is that Christianity has outgrown those acts; Islam has not.