[...]To each their own.
And if you don't care about religion, just leave it alone.[...]
Yes, and to be fair I only brought it up because someone had the brilliant idea to try to use reincarnation as a reason for not eating meat.
That may not have been meant to be taken literally. (As no religion is to be taken to the letter, but that's another debate.) It was probably meant to simply lean towards the notion of compassion for animals.
And I believe vegetarianism and reincarnation are closely related aspects of Hinduism. Which means that for many millions of people, this argument is not irrelevant.
Whether you believe or not in reincarnation, the point is to identify with animals. Which reminds me, aren't we animals too? Carnivorous animals, I grant you. If we can catch preys. If not, we can survive otherwise.
Since I'm going down that road, let's look at primates in general. Most of them are vegetarians, and a few species also eat meat, I believe.
I wonder if back up the ladder of evolution, more species of primates were omnivorous but gave up meat, because it was easier to pick than kill, and they were still sated and healthy. It might depend on the quality of vegetable food available.
Sorry, I'm not going to research that. At least, not now.
To be fair, if I remember my anthropology correctly (I am not an authority on the matter), I think that hunting and meat eating were motors of evolution for human beings. One of the main things that set us apart from other primates and, obviously, put us on top of the food chain.
But that was done already. I'm not sure that eating a lot of meat will give us bigger brains by now. It was mostly the hunting that made a difference, making us develop our brains - added to the energy gain provided by meat in a "survival of the fittest" situation, which is out of date.
Today, the clever thing to do is to have a balanced diet. And that can exclude meat. (I knew a teenager who would slightly ferment his own lentils to give them protein! That's dedicated.)
The fact that many vegetarians are "scrawny" (by your American standards) and "sickly-looking" according to you, might be a natural coincidence: someone who dislikes meat might be someone who dislikes eating a lot and neglects their diet.
Just like someone who reads a lot is likely to be someone who wears glasses. But that is not an absolute rule.