> He who knows only his own side of the case knows little of that. His reasons may be good, and no one may have been able to refute them. But if he is equally unable to refute the reasons on the opposite side, if he does not so much as know what they are, he has no ground for preferring either opinion... Nor is it enough that he should hear the opinions of adversaries from his own teachers, presented as they state them, and accompanied by what they offer as refutations. He must be able to hear them from persons who actually believe them...he must know them in their most plausible and persuasive form.
― John Stuart Mill, On Liberty
A few months back I read "The Righteous Mind: Why Good People Are Divided by Politics and Religion", by Jonathan Haidt. I'd highly suggest reading it for anyone seeking to improve their understanding of the ideological landscape in modern America. From the publisher's summary: In The Righteous Mind, social psychologist Jonathan Haidt explores the origins of our divisions and points the way forward to mutual understanding.
The biggest problem I'm seeing with many online communities is the unwillingness to engage with others. There's no discussions, they just tell you that you're wrong and evil, and then they ban or block you. That's no way to change people's mind; it just makes people more likely to dig in their heels. If you want to change people's views you need to engage them calmly and with respect. One of the greatest example of this that I can think of is Daryl Davis, a black man who converted ~200 people from the KKK just by befriending them.