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.
A murderer is a murderer no matter what the excuse.
BTW, you may have missed it, but you made an appeal to morality in justifying your thought that killing is bad.