I think this author, like many others, gets it wrong by comparing Jesus and Mohammad to try to get at the roots of modern Islamic violence. I don't think you can explain the (relative) non-violence of Christians today vs. the prevalence of violence among certain portions of the Islamic religion by looking at their scriptures.
The reason is that for hundreds of years ago, Christians were the world's crazed terrorists. They would burn you to death for being a heretic, or being gay, or being suspected of witchcraft. When the first Crusade was called by the Pope, hordes of Christians in the Rhine Valley headed north (rather than south and east) to forcibly convert or kill Jews in numerous German communities. The Christian on Christian sectarian violence of the 30 years war was perhaps the worst cataclysm Europe ever endured until the 20th Century.
I am sure Christians would say that such violence is inconsistent with true Christianity, etc. but never-the-less history shows that Christians have no less inherent propensity to religious violence than Muslims. Christians have moved on -- matured, maybe? I am not sure what the word is. Unfortunately, parts of Islam have not, which makes it dangerous today in a way that Christianity is not.