Labelling groups "extremist" without defining the term is problematic.
On the face of it one could label a Muslim as an extremist who advocates democracy, something which the vast majority of Islamic jurists rejected in history.
If you mean by the term their use of violence against states who invade, bomb, torture and extract resource from their countries, then I would say no, it is quite normal in human history for violence to be utilised in such a manner. The more accurate term is probably "freedom fighters" rather than charged terms like "extremists".
If however you refer to the use of violence in a widened battlefield, then maybe; however I would point you to those who forced this situation upon them, the Americans and their allies, a point noted by many political commentators. Targeted assassinations of civilians around the world has set the precedent that the entire planet is a battleground and it is unusual to label the oppressed extremists/terrorists and ignore their counterparts - one cannot isolate one side of a coin from the other.
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