If someone pisses you off, then by all means, be offended. It doesn't mean you get to kill people. Just like if I feel like drinking, I don't have to. It's called impulse control. Which in both the Christian and Muslim worlds seems in short supply.
Image and quote via Slate
The protests were carried out as the publication’s distributors said it was increasing the print run for the first issue of Charlie Hebdo since the attack at its offices to seven million copies when it usually has a circulation of around 60,000. "They offended our Prophet Muhammad. That's what we didn't like," a protester in Niger told Reuters in reference to the cover of the publication that includes a cartoon of Prophet Muhammad.