Would be interesting to see how they qualify "harm". Because sorry, GHB that low? No way. Ecstacy even lower? No way again. Ecstacy in itself, if taken every 3-6 months in small quantities is not harmful, but that just is not reality - and the way 90% do actually take it, large quantities every couple of weeks, is extremely harmful. Believe me, I know. GHB - is often called "liquid ecstacy" in Europe, many times fatal when overdosing or in combination with alcohol.

As for cannabis - I believe that it can be psychologically addictive, but there is imho no real physical harm.

As for alcohol - I never had any doubt whatsoever that it is way more harmful than other drugs - but again only when taken in large quantities and regularly. Somehow, the chance of actually getting hooked on alcohol are far slimmer than on i.e. XTC.

I find it difficult to weigh the different risks against each other. A book very much worth reading: High Society. It raises an intrigueing question - what happens if all drugs are legalized and heavily taxed, as alcohol and tobacco are?