Very well said. One would think of the information age as a way to start better communicating which should break down barriers. But it seems we can just more easily flock to the people who think like we do. So we have more strongly cemented factions.
I find myself getting mildly angry at friends who post things I disagree with. If we were seated together having a beer and he said the same thing we'd keep talking for an hour and I would have no negative feelings. I find if I try to engage online it just goes nowhere. I avoid posting anything other than the most banal things because I don't want to be judged/attacked. I just don't have the time or energy to go in depth to defend my positions. And at this point I could care less if anyone knows what I feel.
It's because of the publicity of the discourse. Normal one-on-one discussions can lead somewhere, because you're not constantly afraid of losing face. When you utter opinions publically, you're sortof forced to stand by them, regardless of their merit. That's why televised political "debate" never ends up changing the opinion of any of the debating parties. They're trying to convince an audience instead of the other party. I think it's a big part of why politicians are so unpopular today.