From an atheist POV watching someone murder a bunch of random people all because of their belief in their God is like watching people standing in line for the next Hobbit movie get murdered all because they're not fans of the Twilight series.  Why would you want to kill people over something so trivial?  And then someone comes along and explains, "Well, you gotta understand the followers of Team Edward are really fuckin serious."  I don't give a shit!  

Then you look closer at Twilight and you see followers of Team Edward and Team Jacob have been brutally butchering each other for years in far greater numbers than from attacking anyone else outside of the Twilight following.  How would you react to how stupid that is?  Because that is literally how I feel about Islam or any other radical religious belief leading to murder.  

And it's not even worth mentioning the original author of the story because this bloodshed was like nothing they had in mind when they created the books in the first place.  Much like whoever the hell put pen to paper thousands of years ago had no idea what kind of bullshit it would lead to today with people butchering each other over how their words are interpreted.  

You want to live in a world where everybody has the same belief system where in your mind it would lead to paradise and peace?  Bullshit.  You just want to live in a world where your belief system isn't challenged, not because it would actually improve anyone's life, which it extremely often doesn't.  You want to kill people just to get people to shut the fuck up about whatever views they have that challenge your own, no matter how matter how radical or innocuous those beliefs might be.  It's pulling the coffee-table-flip on the chess game because you're not having fun and don't want to play anymore.  

It is the ultimate act of selfishness.