It is an unfortunate side-effect of spending too much time online I think. Or online in the wrong spaces.

Everyone has a different tolerance for dealing with unreasonable people, but there is a breaking point for each of us. And if you hit that, you will be prone to throwing your hands in the air, exiting the space where you found these people, and decrying them all to be braindead. I have hit that point multiple times and it has resulted in my making callous generalizations of people after.

It's hard to imagine that people you interact with in an online community are the vocal minority of that community, when you cannot find the silent majority. But I suppose the silent majority doesn't tend to spend time on forums for their viewpoints.