People were always like this. You just weren't able to see it, because you were in an offline "filter bubble" of peaceful and reasonable people. There have been countless civil wars in history after all.
I think the difference is that even if there were unreasonable people, they usually weren't the majority because their reach was severely restricted outside their local area. Now the unreasonable people aren't limited to their geographic area, and can form mobs with members around the world in order to harass people.