It's called polarization, and aside from the truly unbalanced who tend to have absolutist views anyway, it happens when a society grinds to a halt, little gets done, there is a growing unease about how the society is functioning (the extremists give you a well defined enemy to hate), and there is fear of the future. I suppose the question will soon become how do we get past this growing impasse. One political economist I like thinks this is the beginning of the end to the international system which arose out of the end of WWII.
The common fixes as used in the past to correct society's problems are starting to not work so well. The biggest game changer has been globalization. While globalization has offered some definite benefits, one of the downside problems may be that individual countries no longer have the internal control over matters within their borders the way they did 40 or more years ago. That scares people because they are starting to realize they don't really have control. Extremist have people to blame and promise to either create or return to glory days that will fix all. But, the political economist I mention, does not see a collapse. He sees a system which never succeeds, but never really fails. The result is decay, pain, and more decay and more pain. A new system may arise out of this decaying one, but it is going to take widespread participation to start to replace the dying one.
It will also take wise leaders who can see past the current malaise and offer real solutions, but, of course, they will be called nasty names, traitors, sell-outs, a secret plot by the other side of the political spectrum, etc. More than a few think this new system may come out of an emerging localist movement which calls for decentralization of power, but with the proviso that there is maximum participation from all within the identified local area. This movement/idea is in its infancy and doesn't even have political legs as yet, but there are some interesting experiments happening at local levels.