Even our most known thinkers chose Veganism back in the day. This is another wonderful quote from Plutarch on Veganism:
Can you really ask what reason Pythagoras had for abstaining from flesh? For my part I rather wonder both by what accident and in what state of soul or mind the first man did so, touched his mouth to gore and brought his lips to the flesh of a dead creature, he who set forth tables of dead, stale bodies and ventured to call food and nourishment the parts that had little before bellowed and cried, moved and lived.
How could his eyes endure the slaughter when throats were slit and hides flayed and limbs torn from limb? How could his nose endure the stench? How was it that the pollution did not turn away his taste, which made contact with the sores of others and sucked juices and serums from mortal wounds?
It is certainly not lions and wolves that we eat out of self-defense; on the contrary, we ignore these and slaughter harmless,tame creatures without stings or teeth to harm us, creatures that, I swear, Nature appears to have produced for the sake of their beauty and grace…
But nothing abashed us, not the flower-like like tinting of the flesh, not the persuasiveness of the harmonious voice, not the cleanliness of their habits or the unusual intelligence that may be found in the poor wretches. No, for the sake of a little flesh we deprive them of sun, of light, of the duration of life to which they are entitled by birth and being. Source 5j