Thank you, Neil; that appears to be an important downside of Facebook and its ilk -- it becomes an echo chamber that merely increases the intolerance level of its circle for opinions differing from those of the group. Because it is beyond arms' length, the tone deteriorates as well; not only are you wrong but you're a bad person as well.
I do hope you will read my posts here; I have about 90 of my essays posted and a few hundred more to post as I have time -- I'm rather prolific :). Please, if you agree, do recommend me to other readers, like-minded and otherwise as well. I'm quite tolerant.
I like echo chamber, that's a good way of putting it.
The other thing I mentioned in the discussion was confirmation bias, where you assign more importance to something which confirms what you already thought and less so to something which disagrees. So even if you do encounter the odd person with the opposite opinion your brain will filter it out.
Exactly, that's the principle behind your whole point and completely valid.