I would have guessed this was in a very strong sense a linguistic issue. Does a composition "veggie burger" present an oxymoron, thus forcing the consuner to either interpret the composition as being one or the other? Or does the adjective merely make a more specific case? A compiled list of similar compositions would in my opinion help the counter argument.

The line of reasoning of the agricultural lobby about "confused consumers" feels to me like an insult to public's intelligence.

Their arguments about protecting farmers is valid and needs to be considered.