In June of 1989, similarly horrible and grotesque videos and pictures made their way out of the Tiananmen Square massacre, including a graphic shot of the crushed remains of the head of a student run over by a tank. The massacre was unquestionably a terrorist act designed to regain control of the people through their fears by the creation of maximum horror. The government wanted the message to get out. But does anyone really believe it worked for them in the end? Have we sunk so low that we would make the dissemination of such truths illegal today?
ISIL has reached the status of a government. Governments don't have to be recognized to "be". For now, they govern a territory and its people. Like all of the videos of terrorist government atrocities, this video does not generate sympathy for that government. Instead, it builds anger against it.
Furthermore, this man was a journalist. What do you think he would want? Perhaps for the horror of his death to cause change? I'm not a journalist and I know that I'd want the world to see.
"Look! There! Evil!.. pure and simple, total evil from the Eighth Dimension!" -- Buckaroo Banzai