Charlie Hebdo

Points are numbered to make responses easier.

1. Let's start with the basics.  This image should not justify murder. 

It may be disrespectful and distasteful but in a free society, drawing and publishing such a picture should not carry a death sentence.  It also should not carry a fear of prison or fines or any such thing.  Possibly it will bring social penalties but that risk is up to the artist and publisher.
2. A free society depends on the ability to dispute, criticize and ridicule members of authority.  This can be messy but it's necessary.  As Voltaire said, 'To learn who rules over you, simply find out who you are not allowed to criticize.'  No person or institution is granted that position in a free society.
3. Not everyone agrees with the second point.  Here is Anjem Choudary in the US Today, writing about the Charlie Hebdo massacre.

Contrary to popular misconception, Islam does not mean peace but rather means submission to the commands of Allah alone. Therefore, Muslims do not believe in the concept of freedom of expression, as their speech and actions are determined by divine revelation and not based on people's desires.
Although Muslims may not agree about the idea of freedom of expression, even non-Muslims who espouse it say it comes with responsibilities. In an increasingly unstable and insecure world, the potential consequences of insulting the Messenger Muhammad are known to Muslims and non-Muslims alike.

That last sentence seems to say, 'they were warned and they had it coming'.
4. I have no idea how widespread this thought is among Muslims.  Obviously some millions of Muslims live in the US and other countries that share our notion of free speech.  The vast majority of them seem able to deal with the prospect that something personally precious to them may be ridiculed.  Hopefully Mr Choudary's viewpoint is held only by a tiny minority.
5. It would be good for us, and the world as a whole if we could help make that minority even smaller.  As J.S. Mill said, 'If all mankind minus one, were of one opinion, and only one person were of the contrary opinion, mankind would be no more justified in silencing that one person, than he, if had the power, would be justified in silencing mankind.'  We are better off with more and more speech, not less.  Even if that speech makes others uncomfortable or offended.
6. I don't know how good of a job we do really explaining the concept of 'free speech' to the rest of the world.  Of late, we've done a really terrible job of explaining that a commitment to free speech means that listeners just might hear some terrible things.  You might hear things that make you conclude that the speaker is a terrible human being.  You might hear things that make you angry.  You might hear things that make you feel a little sick inside.  Freedom isn't always pretty.
7. What's the alternative?  The only way of avoiding all of the bad stuff is to wall off sections of speech.  This means (per Voltaire's point) figuring out who is in charge and must not be criticized.  It also means (per Mill's point) that minority points of view must be silenced.  An adult society rejects those choices and deals with the possibility of being offended.
8. So how do we communicate this to those who aren't convinced?  By being steadfast in our defense of allowing people to talk.  If someone makes art that is anti-X, we stand up and defend their ability to do so.  We stop looking for ways to tell each other to 'shut up'.  That means terms like 'micro-aggression, mansplaining and privilege' should be used to open up avenues of conversation, not bring it to a halt.  It means a rather thorough reexamination of the concept of 'hate speech'.  Any time we are telling someone else that they must shut up, we give credence to the arguments of someone like Mr Choudary and his belief that people should stop talking in ways that bring him offense.
9. None of this should be taken as saying that people shouldn't criticize speech that they don't agree with.  If you see obscene art, tell the artist and gallery that you find it offensive.  If you read sentiments you disagree with, talk back and explain why you disagree.  This may get messy and loud.  So be it.  That's better than the alternative.
10. Of course, another way of dealing with offensive art and the like is to simply roll your eyes and ignore it.  This is another way that mature, pluralistic societies work together.  They avoid the worst arguments with a sort of 'live and let live' attitude.  We could use more of that.  We'd be better off if we could comfortably go to a restaurant even if we disagreed with the politics of the owner.  We'd be better off if bakers could simply bake cakes without worrying whether they were topped by two brides or two grooms.
11. Large numbers of people can live together with other people who say and do things that they find disagreeable.  We've proved that.  We should be exporting these ideas to any of the rest of the world that will listen to them.