"As I understand it, the rational veggie/vegan choice is "I do not want any part in killing or hurting an animal" (with definition of hurt being very much up for debate)."
I know that veg*ns try to rationalise their diet in these terms but that doesn't hold water for long. For example it's not possible to "hurt" some animal life and the "killing" involved is of the same order of that involved in "killing" vegetables.
For example shellfish don't have a central nervous system and are pretty much the animal equivalent of vegetables. Sea cucumbers, sea urchins, jellyfish are also edible and have no CNS. I don't see veg*ns consuming them, hence there's more to their aversion to eating animal protein than cruelty. There's also not much consideration of the cruelty involved in farming vegetables. Harvesters mangle animals leading to a slow, lingering and painful death. Farmers trap, poison and shoot animals that eat and damage their crops. I don't see much hand-wringing over this from the veg*ns.