While the murders of twelve people at Charlie Hebdo are unjustifiable, one of the killers did attempt, in advance, to justify the attack. The main justification offered was that the attack was in accord with Islamic law. Since I am not a scholar of Islam, I will not address the issue of whether this is true or not. As an ethicist, I will address the matter of moral justification for the killings.
From the standpoint of the killers, the attack on Charlie Hebdo was presumably punishment for the actions of those they killed. In general, punishment is aimed at retaliation for wrongs done, redemption of the wrongdoer or deterrence (this is the RRD model). Presumably the killers were aiming at both retaliation and deterrence and not redemption. From a moral standpoint, both retaliation and deterrence are supposed to be limited by a principle of proportionality.
In the case of retaliation, the punishment should correspond to the alleged crime. The reason for this is that disproportionate retaliation would not “balance the books”, but instead create another wrong that would justify retaliation in response. This, of course, assumes that retaliation is justifiable in general, which can certainly be questioned.
In the case of deterrence, there is also a general presumption in favor of proportionality. The main reason is the same as in retaliation: excessive punishment would seem to, by definition, create another wrong. A standard counter to this is to argue that excessive punishment is acceptable on the grounds of its deterrence value—the greater the punishment, the greater the deterrence.
While this does have a certain appeal, it also runs counter to common moral intuitions. For example, blowing up a student’s car for parking in a faculty parking space at university would certainly deter students, but would be excessive. As another example, having the death penalty for traffic violations would tend to deter such violations, but this certainly seems unacceptable.
There is also the standard utilitarian argument that excessive punishment used for deterrence would create more harm than good. For example, allowing police to execute anyone who resisted arrest would deter resistance, but the harms to citizens and society would certainly seem to outweigh the benefits gained. As such, it seems reasonable to accept that punishment for the purpose of deterrence should be proportional to the offense. There is, of course, still the concern about the deterrence factor. A good guiding principle is that the punishment that aims at deterrence should be sufficient to deter, yet proportional to the offense. Roughly put, deterring the misdeed should not be worse than the misdeed.
In the case of the people at Charlie Hebdo, their alleged offense was their satire of Mohammad and Islam via cartoons. On the face of it, death certainly seems to be a disproportionate punishment. After all, killing someone is certainly vastly more harmful than insulting or offending someone.
A proportional response would have been something along the lines of creating a satirical cartoon of the staff, publishing an article critical of their cartoons or protesting these cartoons. That is, a proportional response to the non-violent expression of a view would be the non-violent expression of an opposing view. Murder would obviously be a vastly disproportionate response.
It could be replied that the punishment was proportional because of the severity of the offense. The challenge is, obviously enough, arguing that the offense was severe enough to warrant death. On the face of it, no cartoon would seem to merit death. After all, no matter how bad a cartoon might be, the worst it can do is offend a person and this would not seem to warrant death. However, it could be argued that the offense is not against just any person, but against God. That is, the crime is blasphemy or something similar. This would provide a potential avenue for justifying a penalty of death. It is to this that I now turn.
Religious thinkers who believe in Hell have long faced the challenge of justifying eternal damnation. After all, as David Hume noted, an infinite punishment for what must be finite offenses is contrary to our principles of justice. That is, even if a person sinned for every second of her life, she could not do enough evil to warrant an infinitely bad, infinitely long punishment. However, there is a clever reply to this claim.
In his classic sermon “Sinners in the Hands of an Angry God”, Jonathan Edwards says of sinners that “justice calls aloud for an infinite punishment of their sins.” Roughly put, he justifies the infinite punishment of sin on the grounds that since God is infinitely good, any sin against God is infinitely bad. As such, the punishment is proportional to the offense: infinite punishment for an infinitely bad crime.
It could be contended that creating cartoons mocking Mohammed and Islam are sins against an infinitely good God, thus warranting an infinite punishment and presumably justifying killing (which is less than infinite punishment). Interestingly, the infinite punishment for sins would seem to render the punishing of sinners here on earth pointless for two reasons. First, if the sinner will be punished infinitely, then punishing him here would not increase his punishment. So, there is no point to it. Second, if the sinner is going to be punished divinely, then punishment here would also be pointless. To use an analogy, imagine if someone proposed having a pre-legal system in which alleged criminals would be tried and, if found guilty, be given pointless and miniscule sentences (such as being mildly scolded for one second). The alleged criminals would then go on to the real legal system for their real punishment. This pre-legal system would obviously be a pointless waste of time and resources. Likewise, if there is divine justice for sins, then punishing them here would be a pointless waste of time.
This, obviously enough, assumes that God is real, that He punishes and that He would punish people for something as minor as a cartoon. It would certainly seem to be a rather petty and insecure God that would be overly concerned about snarky cartoons—people are usually most likely to react to mockery when they are strong enough to punish, but weak enough to be insecure. God, I would think, is far too big to be enraged by cartoons. But, I could be wrong. If I am, though, God will take care of matters and there is thus no reason to kill cartoonists.
If God does not exist, then the cartoons obviously cannot have offended God. In this case, the offense would be against people who believe in a make-believe faith. While such people might be very offended or angry at being mocked, killing the cartoonists would be like enraged Harry Potter fans killing a cartoonist for mocking Daniel Radcliffe with a snarky cartoon. While they might be devoted to the make believe world of Harry Potter and be very protective of Daniel Radcliffe, offensive cartoons mocking a real person and a make believe system would not warrant killing the cartoonist.
As such, if God is real, then He will deal with the offense against Him. As such, there would be no justification for people seeking revenge in His name. If He is not real, then the offense is against the make-believe and this does not warrant killing. Either way, the killings would be completely unjustified.