As white Europeans it is, for the most part, incredibly difficult to grasp why something in someone else's culture could be taken so seriously. But that's because we come from a society that has spent centuries imposing its idea of culture upon countries viewed as woefully inferior. Of course we don't take seriously another country's culture - it's an ingrained attitude.
Off the top of my head I can't think of a single western European country that hasn't chased the idea of empire. I can only think of a couple of eastern European countries that haven't.
So, how can we make it relevant to those of us who don't understand why other cultures don't like their heritage and beliefs being (ab)used in meaningless ways? Think of it this way - one group of people consider something to be rather important and get upset when another group of people treat that same thing with thoughtlessness, disdain or ridicule.
For example, Americans and their flag. It's just a bit of cloth yet look at the anger, hatred and even violence that explodes when another culture says or does something to it. To me it's absolutely unfathomable.
Or how about how seriously people take jazz? Not long after I first joined the forum I posted a funny image of a sign that banned jazz from a nature park. That garnered some quite aggressive responses from those who thought I had absolutely no right to criticise their favourite music.
A friend recently posted an amusing image of the Queen and Philip. Given the context of this post you can probably guess the response he got from certain quarters. How about the artist who changed the poses of former presidents in paintings in the Oval Office? That resulted in accusations of treason and demands for violent retribution.
Gods and religions are cultural. I think we all know that the religious aren't big on being ridiculed or having their gods and/or icons used by non-believers.
How about language? I know I absolutely hate how the English language is viciously and continually raped by those who don't understand either the beauty of it or the necessity to express and write it accurately to be understood. To many others we're just pedantic grammar nazis. France even has a powerful organisation whose sole reason to exist is to protect French from the pollution of other languages. What about food? Just ask Jamie Oliver how seriously Italians take their recipes. Having said that, I recently sent back an alleged Arrabiata to the chef, with a long list of criticisms which included the suggestion that he visits Italy and buys a recipe book that's not written for microwaves, so I understand the Italians fully.
There will always be those who are offended on behalf of someone else, and those who love to wallow in the distress of others, but that doesn't negate the legitimacy of the feelings of those directly offended on the occasions when they actually are, whether you understand them or not.
Personally, I don't know why anyone takes any of this seriously, but I do understand some do and may even adapt my attitude and/or comments accordingly so as not to offend.