Beast Boy: Poster Boy for Squeamish Veganism

Teen Titans member Beast Boy, less frequently known by his orange, lasagne-loving cat monicker "Garfield," is a vegan. His reasoning, as cited in the Cartoon Network animated series:

 I've been most of these animals.

If this is his primary reason for abstaining from delicious bacon, it is one of empathy, rather than quilt over farm conditions or nutrition. Like all vegetarianism, we omnivores have the ability and often the duty to judge this on a logical basis, on the off-chance we ever get into an ethical debate with a fictitious green superhero.

Some background: Garfield Logan got bit by a green monkey. This infected him with a terrible virus, which his parents treated with an untested serum.

Effect: totally not dead.
Side effects: green discoloration of hair, skin, and irises, ability to shapeshift into any animal, living or dead, and depending on incarnation, possibly mythical.

Fact #1 - Beast Boy's powers are not natural, and therefor any attitude resultant of them cannot be defined as "fate" or any other version of the-natural-order-of-things.

The powers themselves, allow Gar to completely change into a different form. He is a complete changeling–"Changeling" actually being one of his aliases–rather than a lesser-classed shapeshifter only capable of changing outward appearance over a human form, Marvel's Mystique, for example. Beast Boy can lose or grow extra limbs, utilize unique organs, even drastically reduce or multiply his own mass, which implies some terrifying dimensional shunting or a whole lot of shed skin lying around. (It also explains his great appetite, and provides him with an advanced healing factor.)

Fact #2 - Garfield does in fact become the animals he transforms into.

Now here's the kicker: within the Teen Titans cartoon in which Beast Boy was very vocally anti-carnivorism, when exposed to chemicals which made his DNA even more unstable and caused him to become highly aggressive and even predatory, the green teen began eating meat. A lot of it.

Though Garfield typically retains his intelligence when transformed, he obviously maintains the innate skills and instincts of the animals he becomes, a sort of animism tempered by rationality. When not in full control of his emotions, Beast Boy leans more strenuously on the brunt-force end of the food chain, and is desirous of meat. This implies:

Fact #3 - Animals totally want to eat each other all the time.

A simple point to prove, typically, but here a coup. If we determine that Beast Boy's powers are unnatural, as is his disdain for consumption of other animals, the only defense left to him is that he, in his "enlightened" position of being a human uniquely suited to empathizing with animals, deems meat murder, but excuses animals for not being aware enough to make this call themselves.

As it turns out, Beast Boy is a condescending speciesist, willing to exploit the talents of other creatures but always live above their ken, on a moral pedestal he has erected for himself. He cares not for the animals we eat, but, like many vegans, for lauding his superiority over anyone within earshot.

"I will eat you, Tofu! I will kill you dead and eat your beany heart."

The other possibility is he's merely incredibly squeamish about what is to him, effectively, closer to cannibalism than omnivorism.