Because if that would incite them to murder they were ready to do it anyway. This just exposes them for what they are. Backing down to their threats would be a far greater recruiting tool.
No, they were not "ready" to do it. That's what incitement means...it means something taunted them to action. We are there to win a war and ultimately mitigate Islamic violence...not purposely incite it and further endanger lives.
If you want to play with our kids' lives, that's up to you. I prefer to fight the necessary battles. These are unnecessary ones; I care more about the welfare of soldiers who are putting their lives on the line every day than a handful of people who want to burn a book to make a statement.