You see this in political discourse all the time

There are lots of smart people on all "sides" of the political spectrum, but in online forums (especially Reddit in my experience) people on dismiss the other side as stupid or evil, rather than trying to see the issue from a different perspective and understand the other persons point of view

I think the anonymity of being online brings out the worst in people. Having a discussion in person tends to be much more civil, even if you completely disagree with the other person