Does God exist

watched a debate online between Joe Boot and college philosophy professors. Great debate very thought provoking. I just had a thought and had to write it down somewhere, so where else than here. Anyways, If evolution believes that we are in nature accidents, so everything we do are dictated by our environments and therefore justifies our actions whatever it may be. Because morality is merely an accident. So if i get angry, and a very justified anger, for example if someone kills my wife or my kids, that action will prevent me from reproduction and is counterproductive to me passing on my genes. Then I in my anger, will desire to kill that someone. Or hurt him/her badly. So am I not justified then according to evolution in my desire and/or action to destroy that person. So how can humans ever promote compassion and forgiveness when such murder or murderous intent is justified?