Different people might justify vegetarianism by citing the suffering of animals, health benefits, environmental impacts, or purely spiritual concerns. As long as there isn't a camp of vegetarians that claim it does not have e.g. redeeming health benefits, we can more or less add all those opinions together.

I think that this is actually very close to the bible/koran example. If people reach similar conclusions from different reasons, they're probably just rationalizing. It would be very surprising if truly independent aspects of vegetarianism all happen to point the same way.

I guess this means that you and I reach the same conclusion about the bible/koran example, but for different reasons ;-)

ETA: I am more negative about vegetarian evidence than James, but I am also more positive about the theists (cf Unknowns, Michael Vassar). In both cases, I say that they are mistaken about why they hold the beliefs they do, but that doesn't necessarily mean the reason is bad. So maybe my position does not apply to my agreement with James.