The internet is just a mirror, and an amplifier
It's a commonplace to observe that the internet is changing the nature of discourse. Many of the concerns raised in such as discussions are, in my opinion, severely over-blown, but it's certainly the case that we can observe changes in behaviour in the real world that can be linked back to discussions in the digital world. The mechanisms of this are somewhat less discussed, but they seem to arise from the very nature of the medium and so will be hard to change quickly.
The future-watcher Ester Dyson once made the following observation:
The Internet is like alcohol in some sense. It accentuates what you would do anyway. If you want to be a loner, you can be more alone. If you want to connect, it makes it easier to connect.Perhaps we can generalise this slightly, and say instead that the internet is both a mirror and an amplifier. It identifies distinctions between people, reinforces and amplifies them.
How does this happen? It begins from the observation that every niche community is globally large. No matter how specialised one's interests, they will be shared by others elsewhere in the world. This has been an enormous boon to many people, most notably those who have (or who have relatives who have) rare illnesses: no matter how rare a condition is in the local gene pool, globally there will be a substantial population in a similar position who can provide understanding, advice and support. Often these will include individuals with access to and understanding of the latest research and treatments, often the scientists and doctors themselves: expertise that can be world-beating, and may completely overshadow what's available locally. What makes such communities possible is the low cost of setting up and maintaining a web site, and the power of search to allow such sites to be found by anyone sufficiently interested in them to spend some time crafting the right search terms. That is, the internet provides for the construction of specialised, distributed, communicating communities such as have never existed before: it's hard to conceive of doing something similar through the postal service, or even the telephone.
So the internet mirrors the human condition, from porn to poetry, and also democratises it. If you want to write poetry, you can hang out in communities that resemble the Bloomsbury Group in terms of their intellectual depth -- and you can do so from wherever you live, limited only by your ability to contribute. You can get feedback on your work or comments from others, perhaps more experienced than yourself, and so improve your own understanding and ability in your chosen field. The same thing has happened since that start of the internet: Conscience of a hacker, a poem of praise of meritocratic technical communities, still resonates with many computer people (including myself).
There is a side-effect of this specialisation, however, that's less positive. By forming a dedicated niche exactly suited to the needs of a particular community, the internet often removes those people from the general forums of discussion. Why engage with a general community when one can be with people exactly in tune with what you want? The answer, sometimes, is that what you want and what you need may be different, and that groupthink is far easier and more prevalent in smaller groups than in larger ones.
This is where amplification kicks in. If everyone in a community is kind of the same as yourself, it's harder to stand out -- and many people love to stand out. You can do so by being more helpful than anyone else, or by be more perceptive and insightful -- or by being more extreme. The very specialisation of internet communities, combined with the ease of communication, the partial or complete anonymity, and the desire to stand out can be very disinhibiting, and can amplify discussion quite quickly to the extremities of what that group considers acceptable. If you hang out in some subcultural chat rooms, what's acceptable is very elastic and discussion will quickly head to the extremes: more extreme than most people can easily imagine, in many cases.
So amplification seems to be a direct result of specialisation -- one of the things that makes internet communities so powerful in the first place -- and can operate both positively and negatively, making the good better and the bad worse.
Actually these effects are becoming more widespread than discussion groups, through the phenomenon of "search bubbles". Google and other search engines now perform substantial pre-processing on search results before presenting them, for example including factors of localisation, user preferences and history. This means that the results you see in response to a search aren't the whole story: you're seeing what Google thinks will be of most relevance and interest to you. This is simply another form of specialisation: more discreet than happens with discussion forums, but still separating out a sub-set of the whole internet's information that's closely targeted to you. This certainly suggests that it might be subject to the same amplification effects, as people perceive (wrongly) that a large amount of content on the internet agrees with them and fits their pre-modelled interests and preferences -- and prejudices.
It's hard to know what to suggest to deal with these issues. Actually I'm inclined to say that nothing should be done, other than to be aware that the mirror magnifies, as it were. The good of specialist communities almost certainly outweighs the disadvantages of these (or other) communities pushing extremism, but it'd be good if those engaged in such discussions keep the amplifying effects of internet discussions in the backs of their minds for when things start to get weird.