Both Western liberals and Western conservatives engage in cultural self-blame, but they do so in different situations, and neither side sees the other side's version of self-blame as valid. This is an important point to remember when pondering the gulf between the modern Western left and right.
When 9/11 occurred, conservatives were enraged to hear leftists like the late postmodernist Jean Baudrillard say that the West had basically caused the fall of the Twin Towers. Something like that rage is occurring now, in the wake of the Charlie Hebdo massacre, as various left-leaning news organs scramble both to denounce the killings in Paris and to denounce the perceived racism and bigotry of Charlie Hebdo's cartoons.
Recently, though, it's been the conservatives who are saying that "this is our fault": the West's lack of backbone in the face of Islamist terror and tyranny; its politically correct fear of being branded racist, culturist, bigoted, etc.; its inability to take strong measures to control immigration and allow in only those who are willing to assimilate legally and peacefully into the larger populace—these things are the cause of the current problem.
So we arrive at a bizarre situation. Whether the West is considered too macho or too wimpy, both liberals and conservatives seem to agree that all of these problems with Islamism are the fault of the West. So why can't we just get along while our civilization crumbles?
ADDENDUM: Let me anticipate an objection from the right: "It's not that the right blames the West for this problem: the right blames the left for this problem. You're conflating." Yes, there's evidence that this objection is true, but there's also evidence that conservative commentators have themselves conflated "left" and "West" in order to issue culture-wide condemnations. A 5-minute Google search will show you what I mean. Upshot: I think both sides need to be clearer about what they're targeting.
ADDENDUM 2: Some very recent examples of the right blaming the West (i.e., all of Western culture) and not specifically the left:
"Ostracized by Cowardly West, Charlie Hebdo Faced the Islamists Alone":
We’ll have to forgive what’s left of the staff at the French satirical magazine Charlie Hebdo if they don’t take much comfort from the ostentatious displays of sympathy and support from their colleagues in the Western media today, and from the similarly defiant words of Western political leaders. For the hysterical reaction of mainstream Western media outlets and politicians to the publication of cartoons mocking Mohammed — first by the Danish newspaper Jyllands-Posten and then by Charlie Hebdo – set the stage for Wednesday’s atrocity.
"The Rush to Blame the Victims in the Charlie Hebdo Massacre":
Liberal societies are those that ceased trying to come to a politically enforceable consensus on metaphysical questions, preferring to tolerate the kookiness of Westboro Baptists if it prevented the cruelty of witch hunts. Better a society of unending offense than unending war.
In the case of attacks like the one on Charlie Hebdo, upholding that principle would require saying that the moral value of a magazine’s publication is not the government’s concern. It has the right to publish what might offend, plain and simple, and the government will uphold that. As for those who would react violently — who would offend against the pact upholding free speech — they, and they alone, are responsible for their actions.
But Western governments are increasingly unwilling to defend this principle, convinced that they can negotiate away, to the satisfaction of their enemies, the offending elements. What they do not realize is that, by doing so, they are negotiating away, too, the open, liberal society that has prevailed for three centuries, and that has, better than any arrangement of persons yet conceived, best assured the security and prosperity of persons.
If it does not remain so, there will be no one to blame but ourselves.
That's two examples, easily found in just a few minutes' searching. A notable exception to the above trend would be Sarah Hoyt, who specifically targets the left: "Je Suis Charlie":
...these asinine cowards, these craven and self-regarding poltroons, started saying things like that the brave men and women who risked their lives for free speech should have been more careful of the feelings of others. These are the same people who routinely, three times a day, post some dig at Christianity, some mockery of Americans, some pseudo-witty comment about Republicans. But see, none of those people threaten to kill them.
The brave social(ist) justice warriors are ever ready to speak truth to the power that will not hurt them. Towards Islam, [on the other hand,] they adopt the crouching position and kiss the [terrorists'] gangrenous blood-soaked pudenda.