When you are able to blame others, then you are able to earn certain rights for yourself. Those rights cannot come to you, if you do not say that others are in a position to harm you. Even the law agrees to killing in self defense.
Blaming is quite nice to the ego. Blaming is a good defense against responsibility. So that you do not have to do the right action; you can just blame somebody. To not to blame is to take the onus of Right action.