How to kill a bear.

When people wanted to kill a bear in the ancient times, they
hung a heavy log over a bowl of honey. The bear would push
the log away in order to eat the honey. The log would swing
back and hit the bear. The bear would become irritated and
push the log even harder, and it would hit him harder in
return. This would continue until the log killed the bear.
People behave in the same way when they return evil of the
evil they receive.