This is a mess larger than I can comprehend, with scores of innocent dead. The spectrum of political issues this crosses is vast. We're talking nationalism, immigration, religion, extremism, surveillance, privacy, and war to name a few.
The nuance required to understand and attack the big picture is almost nowhere to be found.
I saw the French PM said something like "we're at war" - I'm not sure who they're at war with but onward with the endless war.
I've seen plenty of comments about ISIS. It's like a 99.999% chance it's not ISIS - maybe Al Qaeda, maybe a different extremist group. (For why it's probably not ISIS and one of the most fantastic explanations of the what's and whys of ISIS, see [0].) But it shows just how vastly uneducated most people are about the issues that lead to attacks like this.
This breeds calls for extremism in response, like expelling all Muslims (and can only help Trump's campaign) or comments like the one from the French PM above.
I can't imagine being in charge of trying to address all of the underlying issues that feed into attacks like this. And I don't know that those in charge are up to the task.
[0] http://www.theatlantic.com/magazine/archive/2015/03/what-isi...
Edit: ISIS inspired maybe, but not ISIS planned and backed. "During his visit to Mosul in December, Jürgen Todenhöfer interviewed a portly German jihadist and asked whether any of his comrades had returned to Europe to carry out attacks. The jihadist seemed to regard returnees not as soldiers but as dropouts. “The fact is that the returnees from the Islamic State should repent from their return,” he said. “I hope they review their religion.”"
I always stand to be corrected.