Christ never taught that it was wrong to kill in self-defense or in defense of another.  In fact, the Church teaches that "Love toward oneself remains a fundamental principle of morality. Therefore it is legitimate to insist on respect for one's own right to life. * * *  Legitimate defense can be not only a right but a grave duty for one who is responsible for the lives of others. The defense of the common good requires that an unjust aggressor be rendered unable to cause harm. For this reason, those who legitimately hold authority also have the right to use arms to repel aggressors against the civil community entrusted to their responsibility."