There is a thin line between religion or philosophy and fanaticism. And in this clear the need to remember John 8:7: “he that is without sin among you, let him first cast a stone.”
Christians raged religious wars against each others for most of the XVII century. Atheists found in ideas like socialism and the building of a pure race the excuse to commit the worst genocides in the history of mankind. And lest us forget it is good to remember about the millennium of wars between Muslims and Christians for the control of the (not so) "Holly Land", of the gold trade in Africa, of the spice trade to India... Any excuse was good to make a Jesus V Mohammed call for war.
So why are we so shocked about what happened in Paris with the slaughter of 12 people who worked for Charlie Hebdo? Or, by the way, about what is happening in Syria and all over the Middle East with the ISIS?
Basically because we thought we had found in mutual respect for each others' religious or philosophical convictions the tool to better develop them. Nowadays most atheists refuse the idea of sending Christians to gulags (unfortunately not yet in North Korea and China) and Christians refuse the expiation of sins of heresy through fire. We also refuse the idea that violence of any sort should be the mean to convince others of the righteousness of our ideas.
Now what happens with fanatic Muslims is that they are not only bad to non-Muslims, they are bad to the really God-fearing Muslims. To start with the obvious, the majority of the people killed so far by the so called "Islamic Caliphate" have been Muslims. Of course hundreds of thousands of Christians and others were also killed and had to leave their houses, but they are still outnumbered by Muslims.
Besides being killed, the real Muslims also have to fear their reputation tarnished. A bad minority is always much more visible than the invisible good majority. In the same way, as a Catholic I know many truly good priests but all I see in the news of Catholic priests is about the pedophiles. So now all the Muslims have to bear the shame of the fanaticism of some of their brethren.
Having said this, there is one more parallel one can draw between pedophile Catholic priests and terrorist Muslims and that is the silence complicity of their peers. There was in the history of pedophilia in the Church many priests and bishops who, although disapproving the actions of the pedophile few, did nothing to stop them. In the same way there must be around Europe many good Muslims who would never shoot at a cartoonist (or anyone else) but who, knowing of the fanaticism of those few brethren, keep silent. How could the Kouachi brothers buy shotguns and nobody in their inner circle know about it, for example?
Muslim fanaticism can only be vanquished from the inside. It must be the majority of good Muslims going to the mosques around Europe who actively do something to stop the fanatic minority. They must both try to convince them of their wrong ideas and at the same time denounce them to the authorities so they can keep an eye on them.
Hopefully this good majority will also be Charlies now...