Because he tried to have the image scrubbed from the internet. It pissed him off that much. So by everybody posting it in more and more places, it makes it infinately harder to scrub the image from all the places.
You're getting entirely too psychological with it.
"It pisses him off, and this ensures more people will see the image, and save the image, and later spread the image." That's it. That's the end of the thought process.