One day, a wolf saw a lamb drinking water from the same source down at some distance. The cunning wolf thought of a plan to fool the lamb and eat him. So he shouted down at the lamb, "How dare you make the water dirty I am drinking?" "You must be mistaken, sir," Said the poor lamb gently. "The water flows from you to me and not from me to you. so, I am not making the water dirty for you." The wolf began thinking cunningly of some other talk to make an issue. "Do you remember calling me with all sorts of abusive words, just a year ago?" Said the wolf to the lamb. The lamb replied,"But, sir, I was not born a year ago." The wolf said in a loud voice, "Then your father must have abused me long ago." The lamb said,"I apologise on behalf of my father." "You are arguing with me. let me teach you and your family a good lesson", saying this, the wolf jumped upon the poor lamb and killed him and ate him. 
Any excuse will serve a wicked person. 