Because it's a ridiculous premise that you would not apply to any other religion. It's not even a consistent view of Islam; you don't have Islamists in Malaysia (60% islamic) or Turkey (99% Islam) holding the same sort of contempt with to West.
Consider it this way, if a Russian came to you and said "the Ukrainians hate Russians because they are full of Nazis and they hate how Stalin purged Germany of Nazis" you would quickly realize that is ridiculous notion - Ukrainians are currently being bombed by Russian soldiers which fuels their animosity.
The West has largely done the same in the middle east, and not understanding this history leads you down to conclusion that they must hate the West because of Islam. I don't know how you could look at an entire group of people who have been practically waging a war for sovereignty against a incredibly more powerful adversary for almost _60 years_ and come away that their wish to kill westerners comes from breaking their holy law. Yeah, you can pretend Islam is a tiny part of it, but I think a larger part of that hate is having their government overthrown and then having their children blown up in an air strike.