Comment on UPB page 49

Certain preconditions must exist, or be accepted, in order for ethical judgments or theories to have any validity or applicability. Clearly, choice and personal responsibility must both be accepted as axioms. If a rock comes bouncing down a hill and crashes into your car, we do not hold the rock morally responsible, since it has no consciousness, cannot choose, and therefore cannot possess personal responsibility. If the rock dislodged simply as a result of time and geology, then no one is responsible for the resulting harm to your car. If, however, you saw me push the rock out of its position, you would not blame the rock, but rather me. To add a further complication, if it turns out that I dislodged the rock because another man forced me to at gunpoint, you would be far more likely to blame the gun-toting initiator of the situation rather than me. 
Should we count situations of coercion as exceptions to moral principles, or violations, for the purpose of enforcement or self-defense?