It indeed sounds very rational to me... Vegans do not use animal product because they think it's cruel to use animals for this. What wouldn't make any sense is to refuse breast feeding on the same grounds (ie, that it would be cruel for the mother).

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Client: In six days, do you hear me, six days, God made the world. And you are not bloody well capable of making me a pair of trousers in three months!
Tailor: But my dear Sir, my dear Sir, look at the world, and look at my trousers.
(Beckett)