Visceral violent hate of 'heretics' and 'pagans' has less to do with Western civilization and more to do with human nature's propension to identify with a tribe and consider everyone outside the tribe as a threat until proven otherwise.

That propension didn't appear randomly either, it is the result of millenias of hard lessons learned where those outside tribes were indeed threats.

That learned behavior still dictates our actions today, except for some of us, the notion of "tribe" has been enlarged to include a vast number of people, or, for the most idealistic, the entire planet.