If god is dead everything is permissible. Also atheists don't have a concept of sacredness so they don't view human life as sacred.
“A true opium of the people is a belief in nothingness after death – the huge solace of thinking that for our betrayals, greed, cowardice, murders, we are not going to be judged."
Atheism is the opiate of the morally corrupt.
So even if no god exists in reality I should believe it anyway otherwise I lack the ability to be moral?