SB 1.7 - Violence and animal killers
Kṛṣṇa said that Arjuna should not show mercy to Aśvatthāmā, for he had killed innocent boys in their sleep. A person who knows the principles of religion does not kill an enemy who is careless, intoxicated, insane, asleep, afraid or devoid of his chariot. Nor does he kill a boy, a woman, a foolish creature or a surrendered soul. Formerly war was never declared by the whims of selfish leaders; it was carried out on religious principles free from all vices. Violence carried out on religious principles is far superior to so-called non violence.
A cruel person who maintains his existence at the cost of others’ lives deserves to be killed for his own benefit, otherwise he will go down to hell by his own actions. Political morality is to punish a person by death sentence, and this saves that person from going to hell. He will not have to suffer for his act in his next life. Men who are punished on the principle of a life for a life are purified of all their sins, so much so that they may be eligible for being promoted to the heavenly planets. Even the killer of an animal is to be considered a murderer. In the act of killing an animal, there is a conspiracy by the party of sinners, and all of them are liable to be punished. He who gives permission, he who kills the animal, he who sells the killed animal, he who cooks the animal, he who administers the distribution of foodstuff, and he who eats the cooked animal are all murderers, and all of them are liable to be punished by the laws of nature.
For the meat eaters, the scriptures have sanctioned restricted animal sacrifices, and following this procedure is good for both the animal sacrificed and the animal eaters. It is good for the animal because it gets promoted at once to the human form of life after being sacrificed, and the meat eater is saved from grosser types of sins of eating meat supplied by organized slaughter houses.