Dear Kaushik Das, there is something called conscience in every human being. We judge our actions on the basis of benefit for the humanity. Almost two-thirds of all wars fought by humanity was in the name of religion and non-existent gods!
A study conducted in the jails of Sri Lanka some time back revealed that less than one third of one percent (1/3%) criminals were atheists and the rest for adherent followers of various religions. So much for moral teachings of the religions and the so-called holy books!!!!