Your focus is too narrow. Islamists see anyone who doesn't follow their specific view of Islam as infidels...including Islamists with a slightly different view. They kill infidels. Period. It is their ghoulish form of amusement. Any Christian is a target. Arab Islamists kill Black Islamists because them see themselves as superior. See Darfur for examples. Wahabbis see themselves as superior to Sunnis or Shias. They eat their own...and everyone else.
That is because Islam is a theocratic system of government rule established by a conquering warlord.
They are intolerant and will not live under rule of someone who is not a “true believer” (even if that is a different strain of Islam or other “faiths of the book”).
Islamic imperialism is the threat. The Saudis fund the expansion of wahabism in the West. This war has waged for over a thousand years and fuel is being added to the fires.
The world can stand united against it but is unwilling to. And so the battles are taken to be “local” matters only.
There are some who would have been content to let Germany go NAZI as long as they didn’t expand their borders by force.
The Communists used military force and internal revolution to expand the empire and too people were content to say “it’s not my battle”.
Now as America goes Socialist, even Europe says “WHAT ARE YOU DOING?!!!”