What happened at Charlie Hebdo was horrific and sad. Those directly responsible for taking part in or funding the murder of innocent people should be held accountable for their actions.
However, the general populace is being manipulated. Stop to ask yourself why terrorist organizations conduct attacks. Conducting an attack takes funding and other resources. This is why the most damaging attacks tend to come from groups that have had previous high power connections or wealth. For people to spend significant resources to conduct an attack, rationally, we would have to assume that there is some benefit that will be derived by those people "investing" in that attack. The only reasonable answer is that it gives them more power and resources in some way or another. If you don't agree with that answer then you are assuming your enemy is not rationale and you are not taking them seriously.
What do terrorist organizations have to gain by conducting an attack? I.e. how does an attack like this lead to more power and resources for the people who organized it?
Instant notoriety. This is specifically why terrorist groups claim responsibility for an attack. They want to be known as the people who exacted revenge, the people who can get "results" in their circles. There are wealthy, high-power people who don't like the West and, actually, see opportunity in destabilizing western countries. Some of these people have investments or businesses that would stand to gain from western instability. From the perspective of these individuals, when you want instability in the West, who are you going to throw some support behind? Probably the people who are in the news and have a track record of "success".
The pervasive rhetoric after an attack is always divisive. There are a tremendous number of reasons why. It is a self-perpetuating cycle built on differences in moral values in two groups of people. Western culture places high value and emphasis on free speech, prioritizing it above everything else. Muslim culture places high value on modesty, prioritizing it above everything else. These differences in values are at odds with one another.
Islamic terrorists are manipulated by their organizers to believe that violation of their modesty is a capital offense. It must be avenged or all that the terrorists stand for is lost. Unfortunately, people in this group do not have as strong a moral aversion to violence, or more aptly put, they view the articles that Charlie Hebdo published as akin to physical violence. Generally, western culture does not view a violation of modesty at the same level of offence as murder or other violence however often extreme Islam can and does. This is extremist thinking because it takes a group's values and extends them to a point where they are ready to commit violent acts for the sake of preserving them.
Charlie Hebdo are extremists of the opposite faction. They are not violent extremists, but they take the values of their culture to the extreme. They have proven that they are willing to risk violence in order to avoid compromising on their values. That is up to them and 100% their choice. Many people, if asked if they would die to preserve free speech, would probably say "yes". Do they actually mean it though? Are they willing to continue to make themselves a target after their office had been firebombed? Most people would stop after the first firebombing. Charlie Hebdo continued: my argument is that this is also extremist thinking because it takes a group's values and extends them to a point where they are ready to make themselves subject to violent acts for the sake of preserving them.
Neither group will compromise, at all, on their values. Why is this an issue? Democracy as a government relies upon the ability of factions to compromise on divisive issues through rational debate instead of violence. The Islamic terrorist camp is aiming for fractures in Western democracy because, after all, that basis of their funding and resourcing. I do think they get what they want here. One of the main factors is governments need to be viewed as organizations that can protect their people. Look at the police response in France. I'm not saying it's unwarranted, I'm just focusing on the factual result. The government of France needs to look strong and needs to look like it can uphold the values that the French voting population demands. Perpetuation of this divisive rhetoric creates justification for larger security budgets, more secretive government operations and a higher tolerance for privacy violations. These create an imbalance of power between the voting population and the established institutions.
Furthermore, divisive rhetoric puts pressure on moderate muslims to choose a side: either they are leaning on way or they other. Naturally some people lean towards the terrorist side. Additional non-muslims decide that, yes, they agree with muslim values and convert to Islam because they feel pushed to support people of similar values. This feeds muslim terrorist organizations with new recruits for future endeavours.
I'm absolutely not saying discontinue free speech. What I am saying is: what do we stand to gain from kicking the hornets nest? There are reasons why the terrorist organizations want you to. There are reasons why governments in the West don't mind if you do. But what do you, directly, have to gain? Now weigh what you have to gain against what terrorist organizations have to gain: increased funding, increased notoriety and increased number of recruits.
I would rather take this position: 1) Acknowledge my undying right to freedom of speech 2) Refrain from using it, not out of fear but because I don't want to give terrorist organizations more power