Whereas, I suppose someone who simply likes to kill, sans ideology, is better ~ right?
What? No, killing for any irrational reason, be it religion or ideology, is equally evil, stupid and foolish. And history is replete with evil, stupid, and foolish people killing themselves and others because of religion. An atheist might become a mass murderer, but he doesn't kill because his atheism tells him to, he kills because he believes in some other foolish irrational belief, like communism. The religious mass murder, by contrast, does so specifically because he believes that killing is sanctioned by God and religion.