These are all on a spectrum, both in terms of benefits of their use and potential for abuse. You have macronutrients and micronutrients like sugar, fat and vitamins which we all require and most of us take every day without significantly altering our physical or mental state. It seems fine to me to not classify these as drugs of any kind, although it is possible to reach a point where, for example, sugar intake becomes problematic and even pathological:
http://en.wikipedia.org/wiki/Insulin_resistance
Then you have caffeine and alcohol, and that is where things get interesting. They are not considered drugs or legal highs by societal consensus, even though people become physically addicted to them. I don't know what things are like in New Zealand, but more people are killed by drunk driving than marijuana abuse in the US, and yet the latter regularly results in much more severe legal punishments. This is why I don't like the fact that some things are "drugs" or "legal highs" but caffeine and alcohol get a free pass.
Kava is superior to many of these substances, natural and synthetic, because of the profile of its effects and the lack of potential for physical addiction. I would rather advertise that than claim it does not alter consciousness, which is how I interpret the second paragraph. I don't consider kava a supplement like the fish oil pills I take, I drink it because I enjoy how it makes me feel for a short period of time in addition to its long term benefits. In the end, we agree that we shouldn't call it a "legal high," but I don't like saying that it "cannot be likened" to any of these substances.