I think there is - for a start - were it not for humans killing and eating animals - cows and chickens would probably be extinct by now.
I seriously doubt they care much about the future of their species. If they could talk I doubt they would say "Hey, I know you make me wallow in my own $#!T in a cramped pen, and I know you will kill and eat me while I am young and tender, but hey, at least you artificially inseminate me and force me to give birth and take my babies away, ensuring our species continues!"
Not to mention that children and adults would be getting killed left right and center by predators - who would eventually run out of food - and thus also become extinct.
That is waaaaaay out there...like Pluto. I don't know if anything was said about killing in self-defense being wrong, but even if so, we humans have these things called fences. They work.
you seem to focus a lot on the nature of animals - what of the nature of the animal that is man - we are predators. we eat meat
Eating meat does not make you a predator. It makes you a carnivore or an omnivore. Just because you can eat meat does not necessarily mean you should.
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This is mostly true. However, I hope you are selective in where your B12 supplements come from. Many supplements are simply extracts from the livers of slaughtered animals.
Yes, but B12 can be obtained from blood, milk, honey, eggs, fish and shellfish. It can also be obtained from feces. I would say that anyone who cannot fit at least one of those in due to some moral grounds is not quite right in the head. I am sure that one well treated cow could supply enough B12 for a community of 100 people in milk alone, and 100 people could provide a pretty good life for that cow if they chose to.
And who cares about shellfish? Oh, yes! The superstitious!
Honey? Some beekeepers leave plenty for the bees themselves.
It is claimed that apes don't actually require B12 in their actual diet because 1) it is recycled for years on end and 2) because they are so dirty they get it from their own hands.
All told, the B12 argument is not a very compelling one against vegetarianism, as most will still eat something from the list above. The B12 argument is also certainly not a very good argument for every day meat eating. One steak would provide you with enough B12 to last for years, literally.
But as an argument against vegans? Well, vegans just over-think everything. They have good reasons against poor practices, but they usually confuse the poor practices with the practice itself. Anyone against beekeeping on principle is not playing with a full deck.