A bloody nose.

Faith can move mountains is an expression. It describes the power of faith to over-ride obstacles by focusing on a perceived truth as the reason for trying to move the mountain in the first place.
Mankind has developed, alongside its faith a set of philosophical tests to question many subjects that are fundamental to the knowledge of ourselves and the way we think and do things. The questions of what is morality, what is truth, how do we with thought deduce logic. Religion and metaphysics are intertwined and questions pertaining to "free will" are debated without being substantially resolved. 

At some point the question of 'faith' intervenes. Faith a leap in the dark where 'accurate justification' is set aside by the decision, often emotional that something exists which can not be proved but is believed non the less. Religion is the house wherein these faiths reside and because the wish to set aside much of everything we think we stand for is the process of 'believing', it is such a powerful emotional force and we find that discussions about religious belief quite difficult.
The best outcomes are when there is a polite commeradic, "let's agree to differ" parting of the ways but of course what we are doing is shelving a very human debate which in all honesty can only have one answer.
Both sets of views shouldn't exist side by side but of course for harmony we fudge it and attempt to do just that.
In most situations other than an academic test we can get over this hurdle by being decent towards each other and acknowledging that hostility is bad and love is good.  Here though we have the nub of the problem. Faith to the believer is as true and factual as a well trodden thesis is to a non believer and when faith is presented with insult it goes to the core of the belief a person has about their god and it becomes infinitely personal.
If the response is to avenge the insult, no 'rational' can convince the person who has been insulted that there is any justification in what has been done or said and for a minority, revenge is the only answer.
To be honest, perhaps the Jihadist is in the better position since he does not have to swallow the ignominy but rather respond, as used to be traditional, with an act of retribution, "an eye for an eye".
I have often thought that in this PC world which has been thrust upon us we do ourselves no favours by delaying action on a slight, of being forced to allow the slight to go unanswered since all that happens is it festers. If we were sure a bloody nose will defiantly result from our actions then it might make us think twice.