> "This didn't start because anyone threatened anyone."

I'm under the impression that this started when a cartoonist drew a picture of Mohammed, inspiring violent threats from all over. South Park was simply dogpiling on this (as they do with all other contentious issues) - the notable part of South Park's involvement is that Comedy Central actually moved to self-censor.

Well, yes; similarly, if you trace back far enough it started with the evolution of man. But this particular, recent series of events started with the South Park episode, which wasn't responding to any particular event. Rather, it was their 200th episode and they chose to celebrate it by, as they always have, testing the limits of what they can get on TV.