My concern is it sounds like your policy is basically pick on the westerners because they're either cowed or maturely shrug off insults, but don't pick on Muslems because they will react badly. To use your school yard bully example, it's still bullying to pickon the kid who knows he will be tried as an adult for assult (or who has a father with a belt if he gets suspended one more time). The threatened violent protesters are just as much bullies as the artists.
If you wish, to use a more contriversial example, how about abortion doctor shootings? They must be aware that their continued practice will deeply offend people (frequent angry protests, I'm sure they receive threats). Should the doctor be partly responsible, when they are shot? Taking offense does not give someone license to respond with violence or chaos. If we're endowed with inalienable rights (like speech or privacy). It's encumbent on the government to protect the excercise those rights, even in cases where most of the population doesn't agree with the expression.