In Kali-yuga, due to the increase of the modes of passion and ignorance, almost all men are asuric, or demoniac; therefore they are very much fond of eating flesh, and for this end they maintain various kinds of animal slaughterhouses
SB Canto 4
At that time King Purañjana was very much influenced by demoniac propensities. Because of this, his heart became very hard and merciless, and with sharp arrows he killed many innocent animals in the forest, taking no consideration.
When a man becomes too proud of his material position, he tries to enjoy his senses in an unrestricted way, being influenced by the modes of passion and ignorance. He is thus described as asuric, or demoniac. When people are demoniac in spirit, they are not merciful toward the poor animals. Consequently, they maintain various animal slaughterhouses. This is technically called sūnā, or hiṁsā, which means the killing of living beings. In Kali-yuga, due to the increase of the modes of passion and ignorance, almost all men are asuric, or demoniac; therefore they are very much fond of eating flesh, and for this end they maintain various kinds of animal slaughterhouses.
In this age of Kali the propensity for mercy is almost nil. Consequently there is always fighting and wars between men and nations. Men do not understand that because they unrestrictedly kill so many animals, they also must be slaughtered like animals in big wars. This is very much evident in the Western countries. In the West, slaughterhouses are maintained without restriction, and therefore every fifth or tenth year there is a big war in which countless people are slaughtered even more cruelly than the animals. Sometimes during war, soldiers keep their enemies in concentration camps and kill them in very cruel ways. These are reactions brought about by unrestricted animal-killing in the slaughterhouse and by hunters in the forest. Proud, demoniac persons do not know the laws of nature, or the laws of God. Consequently, they unrestrictedly kill poor animals, not caring for them at all. In the Kṛṣṇa consciousness movement, animal-killing is completely prohibited. One is not accepted as a bona fide student in this movement unless he promises to follow the four regulative principles: no animal-killing, no intoxication, no illicit sex and no gambling. This Kṛṣṇa consciousness movement is the only means by which the sinful activities of men in this Kali-yuga can be counteracted.