The answer
For St. Ambrose, self-defense is unacceptable because it inevitably destroys the virtue of love, which is also known as godliness, and is thus the virtue that unites the person with God and is the foundation of all other virtues.998
Fr. Tadros Yacoub Malaty
Notes
998 St. Ambrose of Milan, Discourse on Ps. 118:18:45; On Ps. 36:37.