ok, the point of the whole thing is that the most tame, most innocuous image of Mohamed is (as of some time around 2004) supposedly justification of murder.
How about asking yourself why they are seriously offended? What cultural, societal, and anthropological elements lead to such violent reaction to simple religious depictions?
The "answer" would turn into an academic study, no resolution, and fixes nothing. That being said, Free Speech is, and always has been a double-edged sword. If you say something, get ready to defend yourself on both criticism and responsibility for said actions. People can and will be offended, happens here, happens there, for the same or different reasons.
Attempting to use that [murder] justification is a red herring, appealing to emotional statement of murder simply dodges the problem of analysis. In this matter, it's knowing when you're trying make a valid point, which I see nothing more than a mere jest for quick kicks, not a solid examination and viable solutions.