I think it goes a little deeper than that, though, Faheem. When I said that I can't pretend to understand the mindset, I had in mind my miniscule, rudimentary understanding of the impact on Muslims from the Middle East on the fact that they largely come from a ethnic culture that derives a huge portion of its identity from religion. Islam isn't just a religion; it is probably the primary influence on their culture (even on those there who aren't Muslim). I suspect that this makes it much easier for violence to result from a caricature of their prophet.
I obviously will never understand the impact of over 1400 years of cultural influence on how strongly a group can feel about something like this. But to me, anytime you engage in acts that lead to death, there ought to be a "justification," more than just an explanation or a cause. Otherwise, why have a problem with what we're doing in Iraq? It's "caused," and "explained," but certainly not justified. If I didn't need a justification, I wouldn't care what Bush & Co are doing there, or are planning to do in Iran. And no, you don't need to justify it, and I don't. But if no one else can, then I can't be non-critical about it.