The extremists of one side need the extremists of the opposite side to ensure their survival. They, while apparently trying to defeat each other, subconsciously and many times consciously support each other (in a paradoxical fashion) as the growing strength of their adversaries is a justification for the growth of thier own strength.
Re: A simple truth: Exremism feeds on extremism
Extremism may be dealt with moderation too but it takes a lot of time and efforts and can cost a lot more. For politicians and leading business-operators time and money counts more than unsettled disputes left behind extremism and handling it with that.
Re: A simple truth: Exremism feeds on extremism
'Extremism feeds on extremism', not necessarily.
If we consider those who appose the prophets, for example the Meccans who were hell bent against the Holy Prophet (saw) were just like the extremists of today if not more, yet the Holy Prophet (saw) didn't chose to follow their actions as a reaction to extremism. Their extremism fed on hate!