The symbolism of meat-eating is never neutral. To himself, the meat-eater seems to be eating life. To the vegetarian, he seems to be eating death. There is a kind of gestalt-shift between the two positions which makes it hard to change, and hard to raise questions on the matter at all without becoming embattled.
What great philosophers do for us is not to hand out such an all-purpose system. It is to light up and clarify some special aspect of life, to supply conceptual tools which will do a certain necessary kind of work. Wide though that area of work may be, it is never the whole, and all ideas lose their proper power when they are used out of their appropriate context. That is why one great philosopher does not necessarily displace another, why there is room for all of them and a great many more whom we do not have yet.
By contrast, if one conceives the idea of human rights as centring on the notion that each individual is completely autonomous and should have entire control over its own fate, this seems to me unrealistic even for human beings, and far too one-sided to be used as a central tool of morality.