If ever Mohammad would have lived in our modern world, he would have been considered as a vengeful, macho psychopath, who ordered the beheading of countless people "just because they offended him". Such was the price of his own pride.
Whether they existed or not, we are far, very far away of the morality preached by Zoroaster, Bouddha or Jesus. Islam is incredibly violent, compared to its rivals, and what is really frightening is the fact that this violence is deeply embedded within the Quran and the immutable shariah. Islam is the only major religion that fully legitimize the use of violence, slavery and lies, if circumstances ask it.
For instance, this debate on slavery within the Islamic world is simply surreal. The Islamic world and civilization has been entirely BASED on slavery, on an almost industrial and societal scale, much more than the Western World have ever been. For Africa only, the Arab slave trade drained almost twice the number of human beings than the West did. And those slaves were treated even more cruelly than in the Caribbean plantations (a lot less survived). And of course, you have to add dozens of million of slaves abducted in Europe and India as well.
As a matter of fact, historians can follow the progress of slavery through early middle age thanks to Islam, which introduced this practice once again in countries where it just had been abolished.
As a liberal atheist, I do not like religions or ideologies, but some are definitely worse than the others, especially when their values are unable to evolve during millenias. While there is a faint hope of redemption with Shia Islam (because it allows Itjihad), there is NONE so far with Sunni schools like malekism and hanbalism.