> Even the most devout vegan would surely concede that the plants they eat must die in order to render sustenance from them.

Let me (far from a vegan) try to disagree: you can sustainably harvest the fruit or the bark of a plant without killing it, and you can certainly argue that those parts aren't alive in themselves. You could stretch the argument to include the sap and the leaves. Does a mother have to die to suckle her baby?

A really enlightened follower of this argument might limit himself not only to renewable parts of the plant, but also of animals: it's OK to eat eggs, dairy products, honey, blood pudding, but not meat, potatoes or carrots.

Of course, we don't farm those products in a way consistent with not killing the non-productive animals, with the possible exception of honey. But in principle one could.