Ramadan: Why do extremist think that they are better,when in hadith it says for us to be moderate?

First of all, please do not confuse extremists with terrorists. Extremism has existed in just about every religion, including Islam, but did not always result in violence. Secondly, "moderacy" is relative. Your moderate views might be somebody else's extreme liberalism. Finally, I would say that moderacy comes from broad education, which we are lacking just about everywhere.