The basic political principle of the Objectivist ethics is: no man may initiate the use of physical force against others. No man — or group or society or government — has the right to assume the role of a criminal and initiate the use of physical compulsion against any man. Men have the right to use physical force only in retaliation and only against those who initiate its use. The ethical principle involved is simple and clear-cut: it is the difference between murder and self-defense. A holdup man seeks to gain a value, wealth, by killing his victim; the victim does not grow richer by killing a holdup man. The principle is: no man may obtain any values from others by resorting to physical force.
It is only as retaliation that force may be used and only against the man who starts its use. No, I do not share his evil or sink to his concept of morality: I merely grant him his choice, destruction, the only destruction he had the right to choose: his own. He uses force to seize a value; I use it only to destroy destruction.