Vegan is a word coined by Watson in 1944. It is a neologism. As such it is subject to rapid evolution in meaning that is known to be the fate of neologisms:
http://en.wikipedia.org/wiki/Neologism#Evolution_of_neologisms
I suggest that it is a strategic mistake for the abolition movement to use this word as a significant part of its rhetoric because the movement cannot control how the word's meaning will evolve. Because the larger society is the principle influence on the evolution of our language, it is likely that the word "vegan" will become increasingly welfarist in meaning. It is peferable to use rhetoric that is not subject to reinterpretation or distortion, such as "the non-use and non-ownership of animals".
I think, though, that it is extensively used in the movement precisely because it is easily reinterpreted to mean what the user desires it to mean, so it can serve as a shield against more critical scrutiny. For instance, it's easy for me to say at work that I am vegan because it allows me to be vague about exactly what that implies. Whereas it would be much more problematic for me to say at work that I am opposed to the use and ownership of animals.
This defensive posture may be useful to us in mixed social situations, but is counterproductive for the movement to be this vague in its rhetoric. The word "vegan" should not be used at all in statements on abolition and should be replaced with the most explicit and descriptive alternative consisting of words of well-established and unambiguous meaning in every case. It would be a waste of time for the movement to attempt to control the meaning of the word.

