There is a difference in worldview between Biblical Christianity and Islam. The major difference at its core is deeply spiritual. This variance is as deep and drastic as the teachings and lives of Jesus and the Apostles as compared to Muhammad and his immediate successors.
All Muslim groups, including the Jihadis, see themselves as good Muslims. This is a most important point. Even the most violent Muslim groups see themselves as good Muslims. They believe they are being obedient to the words in the Qur’an and the traditions of Muhammad. Therefore if any Muslim group, Sunni or Shi’a, deviate or attack another Muslim group then that Muslim group must be bad. If you are a pious and practicing Muslim and other Muslims disagree with your group or attack your group then they must be bad or takfir. This perspective incentivizes the “good Muslims” to attack the bad Muslims. This helps explain how a Sunni Jordanian pilot was burned to death by ISIS. Since ISIS adherents see themselves as good the Jordanian pilot who bombed them could not possibly be a good Muslim. He was then treated as a heretic. Since Muslims who disagree with another Muslim sect are viewed as bad/misguided then this assures unending conflict between Muslims and with non-Muslims. This also helps explain why many Muslims feel they must defend Islam despite the facts. The quote below is often repeated.