I think sentient is probably closer to his definition. Yes, vegetables are 'alive', but (as current knowledge) they do not feel. Which reduces the apprehension of eating it.
As a worse example of the same path, castration of bulls has always been seen as "OK" for convenience in raising beef, none the less I'm thinking a somewhat higher "brain-ectomy" of livestock isn't going to fix everything up for vegetarians.
Well of course not. You're still ending a sentient life. You're just separate out the sentience ending from the life ending.
Obviously, being such a common practice.