It's something for them to throw back at the West to try to justify their violence against innocents.
It's also used by liberal/progressive types to justify the action of the terrorists on the grounds that they were oppressed, downtrodden, victims segregated from society at large, and therefore it is understandable that they would act out violently--essentially blaming the victims for their own deaths. "Little Eiechmanns" comes to mind.
What the apologists fail to understand, or more likely deliberately ignore, is that in most Western countries, including the USA, Britain, and France, the Muslims tend to form insular enclaves with their own schools and stores and entertainment and lifestyle. You have the Somali enclaves in the Minneapolis area, a large Muslim population in Dearborn, and similar communities in Britain and France. Children born in these enclaves are usually educated in Muslim schools, and don't see much of the outside world, unless their parents are secular/non-practicing Muslims. In many cases, these enclaves bring the dysfunctional social institutions of the parent country (honor killings, sexual assaults, etc.) with them. But when that self-imposed isolation from the host society causes economic and social disadvantages, they blame the host society for not being tolerant/open enough, and cast it as a historical continuation of the Crusades, which they cast as wars of Muslim oppression (conveniently forgetting the centuries of Muslim conquests that preceded the Crusades).
The Charlie Hebdo kind of crap will continue to go on until everyone is willing to call a spade a spade, and recognize that the jihadis have declared war against all of us, that their motivations are based on a dysfunctional religion, that they do not fear death, and they will not stop until they are all killed, or we all bend knee to Allah.