In the discussion I'm seeing there's a lot of slippage between mealy-mouthed apologism (distasteful), downright casting of blame at French society (offensive) and talking practically about the origins of the violent ideological sentiments of suicide bombers and also IS's own base of infrastructure and support.
The article from September that Gurgen linked provided some real insights into the banlieues, but also repeatedly alerts you that poverty and hardship are not uniformly found in the backgrounds of jihadis and foreign fighters. There is more going on.
Meanwhile, this morning it has been reported that the French government has announced that the Syrian passports found on the bodies of attackers were fake—they had not been hidden among the flux of refugees into Europe. The mutually enablling political dialogue between Islamic State and the xenophobic right in Europe could not be clearer. Each grows based on the influence of the other.
Regarding "western imperialism"—the accounting of right and wrong aside, to speak with moral authority to an international audience about the deaths of its own civilians, the western world needs to take honest ownership of the civilian casualties its military campaigns inflict overseas, reckoned at over a million Muslims (at a minimum) in different countries in the past two decades.