Upon reflection, I think that the "graphic" nature of the photo is not in the severed head itself. We have seen much worse in movies. Rather, it is the non-graphical realization of the viewer that this is for real...it's not pretend and that there is a evil eminating from it.
The stupid Jihadists in the Philippines were circulating a snuff video of their exploits. One of which was to behead a Philippino soldier. The Philippine government showed this video on national TV and it resulted in a wave of revulsion at their local Islamic Jihad.
The leftists in the Philippines tried to block it being shown. The leftists and the Islamics seem to get along just fine in so many instances. Leftists like to provide the cover for Islamic Jihad and brutality. Through multiculturalism and other nutball ideas.