Did Charlie Hebdo act irresponsibly by publishing the cartoons?

A number of commentators on the Charlie Hebdo killings, have suggested that Charlie Hebdo acted irresponsibly by publishing cartoons of the prophet Muhammad, given that they must have known such cartoons might provoke a violent backlash. Tony Barber at the FT wrote:

Charlie Hebdo has a long record of mocking, baiting and needling French Muslims. If the magazine stops just short of outright insults, it is nevertheless not the most convincing champion of the principle of freedom of speech. France is the land of Voltaire, but too often editorial foolishness has prevailed at Charlie Hebdo.  

This is not in the slightest to condone the murderers, who must be caught and punished, or to suggest that freedom of expression should not extend to satirical portrayals of religion. It is merely to say that some common sense would be useful at publications such as Charlie Hebdo, and Denmark's Jyllands-Posten, which purport to strike a blow for freedom when they provoke Muslims, but are actually just being stupid.

And the Muslim cleric Anjem Choudary wrote:

The truth is that Western governments are content to sacrifice liberties and freedoms when being complicit to torture and rendition — or when restricting the freedom of movement of Muslims, under the guise of protecting national security.

So why in this case did the French government allow the magazine Charlie Hebdo to continue to provoke Muslims, thereby placing the sanctity of its citizens at risk?

It is obviously true that, insofar as many Muslims are deeply offended by depictions of the prophet Muhammad, and extremists have reacted violently to such depictions in the past, Charlie Hebdo were putting themselves at risk by publishing the cartoons. In the sense that they chose to do something that much evidence suggested would be likely to provoke an attack, they could reasonably be called irresponsible. By analogy, a person who brandished a wad of 50s in the middle of a bad neighbourhood and then got mugged could reasonably be called irresponsible.

Importantly, however, to have acted irresponsibly in this sense is not to be blame-worthy or at fault. If a Muslim woman wearing a burqa were attacked by an irate anti-sexist, we would not say she was blame-worthy or at fault, even though she could reasonably be called irresponsible for choosing to wear a garment that some people find deeply offensive.