A publisher published something that offended. It mocked, it offended, and it showed the fallacy of a religion. It angered.
So the terrorists decided they needed to publicly destroy and ruin the publisher in a way that would not only make that destruction a public spectacle, but do it so spectacularly that others would think twice before publishing or saying anything similar.
The terrorist wants to sow fear. The destruction of an individual is not just meant to be a tool of vengeance, but a tool of instruction. It shows others what will happen to them if they dare do the same. It is generates self-regulating peer pressure. Others, fearing the fall out, will being to self-police and self-regulate. They will silence others on behalf of the terrorists. Out of fear, they will drive the ideas from the public square and society will make them off limits.
It is not because the ideas are bad, but because the ideas offend a group that can destroy and tear down.
So when a publisher published something that mocked and offended a group prone to offense at such things, something had to happen.
The terrorists did what had to be done to publicly destroy and ruin the offender.
So they demanded the Mayor of Atlanta fire the Chief of the Fire Department for daring to write that his first duty was to "glory God" and that any sex outside of heterosexual marriage was a sin.
And the terrorists won in Atlanta.