Oh, yes, it is bothersome when certain folks claim "moral high ground" for being vegetarian. However, it is bothersome in general when someone claims "moral high ground" no matter what the topic or subject is, because the very idea of "moral high ground" is problematic. Some of this is owed to my moral nihilism; there's no such thing as a moral or immoral action in the first place, much less "higher" and "lower" ground to stand on. In terms of virtue, however, fussing about who has the supposed "higher" ground suggests some rather questionable values. I suppose if one considers it a virtue to win all things one regards as a competition it might make sense to fuss about having the "moral high ground," but to my mind, this does a grave disservice to the heart of the matter. One should be upholding a given value because one believes it to be worthy, not because one feels a need to be "better" than one's fellows.