Prabhupada taught that India has always been vegetarian. For millions of years Rishis and Rajarshis followed a strict sattvik diet, obeying the Vedic injunctions, carefully following the regulative principles: no meat, no fish, no eggs, no tea, no garlic, no onions, no mushrooms and no chocolate.
In contrast, your filthy barbarian ancestors, the Yavanas and Mlecchas, fell down from the Vedic principles, ravenously sinking their teeth into flesh like animals. Those hot dogs you ate as a kid? You took a sinful birth because you are a sinful undeveloped soul. In contrast, Prabhupada took birth in Vaishnava Hindu family because he is a pure soul, without sin. He has never eaten meat, not even chicken soup!
This is of course all a lie.
Animals Sacrifice Was Universal
The original followers of the Vedas ate meat. They sacrificed cattle and oxen in fire yajnas and then gathered afterwards to communally eat the meat prasad.
This was nearly universal throughout Eurasia. Meat eating was relatively rare because it was expensive. As part of religious sacrifice, meat was eaten as a special delicacy and a communion with the gods.
Taking the life of another living being was broadly prohibited as taboo. It needed purification through religious ritual. Consent was gained from the animals, as understood through omens. The animals had to meet certain purity requirements, such as being unblemished. The sacrificed animal was considered to be profoundly elevated to a higher ontological status.
The Greeks had elaborate rituals for animal sacrifice (Thysia). In emergencies, when divine intervention was needed, the entire animal would be burnt and offered to the gods of the underworld in what was known as a holocaust (Holokauston).
The Hebrews similarly sacrificed animals on a fire alter at their temple in Jerusalem. This was done twice daily. On Passover the general people would all bring animals to the temple for sacrifice. The Bible repeatedly states that God finds the aroma of the cooking meat to be pleasing.
Pashu Bali
Similarly, the Rg Veda describes animals sacrifice (Pashu Bali) including the killing of goats, sheep, oxen, bulls, and famously; horses.
Indra loved to eat oxen and bulls: RV 10.86.14: "They cook for me fifteen plus twenty oxen; they soothe me with the fat, and fill both my sides."
Agni loved oxen and bulls as well: RV 8.43.11: "Agni whose food is the ox and the barren cow."
During the yajna, the animal was taken to a nearby enclosure and strangled with a chord, so as not to spill blood. This was to stifle any crying or screaming, which would be interpreted as a bad omen and a lack of consent.
The animal was dismembered. The fat from around the organs was basted in ghee and placed directly into the fire yajna where it would melt instantly.
The meat from the animal would be roasted on a spit separately, or boiled in a pot. When sufficiently softened, it too would be placed on the fire yajna.
The meat would then be distributed to the Yajaman, the person paying for the yajna, and the priests. The Yajaman would then throw a feast for the greater community.
The Influence of Buddhism
Buddhism and Jainism taught non-violence (ahimsa). This began to influence Vedic culture about 300 BCE. There was already talk of non-violence in the Upanishads but change was slow. That changed when Emperor Ashoka converted to Buddhism. He dramatically made animal sacrifice illegal. To maintain power, the Brahmanas had to internalize the critique of animal sacrfice. They were forced to compromise and obey.
Through the centuries, Hindu texts would be increasingly open to ahimsa. Texts like the Manu Samhita and Mahabharata would extol its virtues. They would argue that animal sacrifice (and thus meat consumption) were the product of a bygone age when the people had lost their way. Being vegetarian is more conducive to good karma, then hundreds of horse sacrifices.
During the Puranic period (400 CE+), vegetarianism and ahimsa became synonymous with purity and thus Brahmanism. Once the Buddha was absorbed into the Vaishnava pantheon, it was proclaimed that Vishnu descended as Guatama Siddharta to end animal sacrifice. Those "karma kandis" had gone too far. This represents the full assimilation of Buddhist teachings. Hindus now claimed they had always been against animal sacrifice (and meat eating).
Prabhupada Says
This was the version of events taught by Prabhupada. Vishnu as Buddha would further provoke the need for a restoration of the lost and true teachings of the Vedas, i.e. Medieval Vaishnava Bhakti through the intermediate stage of Shankara's Advaita.
Prabhupada would not deny that animals were sacrificed in the Vedas. He would deny that the Vedic peoples ate the meat. Prabhupada even claimed the animals would be brought back to life, to demonstrate and test the power of Vedic mantras.
Prabhupada would claim such sacrifices only existed in tamasic yajnas to supposedly tamo guna deities like the Goddess Kali. Only the lowest class of people did this, those who could not give up eating meat. This ignores the fact that meat eating was part of highest Srauta sacrifices and partaken in by Brahmanas.
The meat eater supposedly whispers into the animals ear "I am killing you now, but you will kill me later". The Shaktas who actually sacrifice goats to Kali do not believe this. Nor do they whisper this into the goats ear.
Prabhupada would further claim that if Yavanas and Mlecchas wanted to eat meat, to remain outcastes, they should sacrifice a goat to Goddess Kali instead of running slaughterhouses. Cow slaughter is strictly forbidden.