This has already been discussed but in summary:
We have nothing against people adopting dietary veganism, it is great. But veganism is a lifestyle choice that excludes all exploitation and use of animals as far as is practical. So what you eat is part of veganism but so is what you wear and the toiletries you use. Dietary veganism does not encompass the full meaning of veganism. You say that we don't own the word 'vegan' but it describes our lifestyle, not someone elses diet. Using it this way takes it away from those who follow its full and proper definition.
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