True, it's something I find hard to grasp, I have a Spanish friend, and we have very opposing political views.
We know this of each other, yet we are capable of each giving their point of view, and there are no rows about this.
This is how it should be, I think.
But it feels to me that many people are not up to that standard.
There can be many reasons as to how rows develop. Often it's because emotion is the overriding driving force coupled with an almost fervent desire to protect their sacred beliefs at any costs. By sacred by the way, I don't just mean that of a religious nature , but rather any sort of ideals which someone may be strigently locked into.
Then of course, you may get one or more individuals whipping up the room with their opinions/beliefs and so eventually creating such a febrile atmosphere, you'll get a wolf pack mentality developing leading to those holding differing views to be targets to be attacked.
For the record, I like to point out that I'm no saint and in no way trying to portray a holier than thou impressio. , I've been caught up myself with this is in the past and also, for those holding and openly displaying hateful, harmful, cruel views, then I'm likely to loose my honeysuckle just like the next man.