Ideology...

Ideologies seem to be destined to stand in conflict with each other, to create tension between each other and then ultimately go to war. Why is that? People that believe in their ideology most often believe that all other ideologies are wrong and are willing to kill for their ideology and often are willing to die for it as well. Yet, why do ideologies necessarily confront each other? Ideologies aim to answer many questions and often do so in a way which does not allow for different answers. This creates friction when two different ideologies meet each other, each explaining the world and certain other things in its own ways. The ideologies 'threaten' each other by simply supplying a different point of view. But do ideologies have to 'feel threatened' by each other? Is it impossible for ideologies to coexist?