Quran (3:151) - "Soon shall We cast terror into the hearts of the Unbelievers, for that they joined companions with Allah, for which He had sent no authority". This speaks directly of polytheists, yet it also includes Christians, since they believe in the Trinity (ie. what Muhammad incorrectly believed to be 'joining companions to Allah').
Muhammed was a general leading an army in 600 AD. He made war and conquered a big empire. He killed thousands of civilians and took the women as sexslaves. Islam was spread with the sword and war.
ISIS are true muslims, they live their life like Muhammed. Making war and conquering until all has submitted to Allah. Allah means submission.
Muslims who are not part of ISIS are fake muslims. They do not live like Muhammed. They don't follow the Quran even. Ignorant little ones.