I have known people who lost their faith in God during the Holocaust, and others who kept it. But that anyone can have faith in humanity after Auschwitz to me defies belief. -
(Jonathan Sacks)
Much has been expressed by others. From peter matthiessen in his novel on auschwitz called "in paradise". Such as citing auschwitz-birkenau as all the proof that as a species the human animal has never lost the most primitive predator-scavenger on the savannah, the incipient killer.
I have total faith that humans will continue to kill each other en masse just as they always have. The question is how do we understand and live with human nature.
The question of faith in God is something else. Maybe shedding ones faith in God is a positive step because Ultimate Reality is not about faith or belief. Nature is what it is regardless of our shallow opinions.