Mussolini was not an athiest. He brokered the deal between the Italian government and the Catholic Church that solved a rift that had been in place since Italian unification. And he was very Catholic.

Stalin, Kim Jong-Il and Mao did not kill in the [i]name[/i] of atheism. Neither did Dahlmer. What makes a crime a crime of religious extremism as opposed to a crime of just stupid nutfuckery (Dalhmer) or political oppression (Mao, Stalin, KJ-I)