To take one small matter, fascism was marked by extreme nationalism and generally white racism. Islamic extremism contains neither element--the Islamists want to destroy all nations and unite the world under a caliphate and they are, obviously, not white racists.
So it's a version of Islamic "anti-religious everything that isn't Islam fascism", totalitarianism, or whatever other word you would prefer to use. So what if it's a made up word? Does that really matter other than semantically? Would it be Islamist or Islamics? I know what their goals, unstated or stated, are for the world at large. Which is exactly why we need to squash this movement with extreme prejudice. Peace through superior firepower. A great Briton understood this "movement" -- Winston Churchill and we are suffering for not listening to him then.