If you look at some of their cartoons, yes, I can see how they can be insulting or irreverent. I mean, look at this cartoon below of a Jew and a Nazi kissing, and it says "Judeo-Nazism: Love is stronger than hate."
Can you see how this would anger more than a few Jews, and how it can be perceived as anti-Semitism? I do. It infuriates me to no end that someone would be that insensitive. However, do you see Jews going out and assassinating the cartoonists simply because they find it insulting? Nope. There is only one religion whose practitioners will go out and kill someone because they can't take a joke: Islam. Why is it that there is not a single imam of clout that speaks out against such depravity? The better response to insulting cartoons is a non-violent one (e.g., boycotting) and to call a spade a spade, much like with the "Death of Klinghoffer" controversy a few months back.
I'm not going to be the least bit surprised if someone blames the attack on Islamophobia. To suggest that the satire brought about the attack is similar to blaming a woman for being raped because she was scantily clad. It's not the fault of Charlie Hebdo; it's the fault of the perpetrators who decided to murder in the name of Islam. It is attacks such as these that perpetuate stereotypes of Islam. If you want people to stop having negative views about Islam, Muslims in developed nations should use their freedom of speech to speak out against these depravities.
And it's not just Muslims who should use their free speech to speak against such immorality. We should double down and continue to use our freedoms of speech and press. We shouldn't be afraid to use our freedom of speech just because some religious extremists are offended. If we do become afraid, then anti-intellectual, ignorant ignoramuses who like to censor free thought win. In a free society, freedom of press needs to prevail, especially since it "contributes to good government, self empowerment, and eradicating poverty." Without it, we become slaves to fear and authoritarian prudes who lack a sense of humor they sorely need.
Aujourd'hui, nous sommes tous français.