Because Apple has a lot of respect for life itself. They also blocked a (non-offensive) app designed to call attention to drone strikes last year. You know, the American attacks that kill 10+ people for every "enemy" that they get:
Apple Rejects Drone-Strike App

Even more censorship, this time involving environmental causes:
http://www.hollywoodreporter.com/news/filmmaker-accuses-apple-censorship-promised-land-event-400193

Fawk Apple.