This is similar to my belief as to why modern American politics is the way it is. It's so much left vs right, red vs blue, etc.

During the cold war, we had a common enemy in communism. Sure there were disagreements, arguments, fights, but at the end of the day, most everyone could agree that we had to stand up for America.

Now those common enemies aren't such a threat, so we look across the aisle for our enemy.

It used to be "we just have different visions for America but we all want to succeed" and now it's "OMG you are trampling my right to ___________ you Nazi!".

Your comment says all this much better than I ever could, though.