I have amazing skin and hair quality when I include a whole avocado in my diet most days of the week. the more expensive organic ones from high end grocery stores are actually better than the cheap ones. I used to also do the crazy thing with a vitamix blender where I blend up the whole seed and drink it with no ill effects and actually recall feeling quite good when I drank those. Not sure if it's actually safe to do that with any frequency but there is some interesting literature about it on pubmed.
There's a study that shows rats fed a diet of 10% unrefined avocado oil had a tendency for liver fibrosis compared to the rats fed the same amount of refined avocado oil, though. The interesting thing is although unrefined avocado oil tended to promote liver fibrosis in this study, the same type of study done by the same authors previous to the liver study showed that unrefined avocado oil actually made skin less prone to fibrosis.
I have a feeling that the potential negative effects of unrefined avocado oils on human liver is not bad, in the real world, at reasonable intakes. Especially with people drinking coffee and getting taurine etc. Furthermore, there is another recent study on rats on the specific portion of the avocado oil that is removed after refining, which show it actually helps their livers by protecting the mitochondria from oxidative damage. I haven't done an in-depth enough reading to figure out how to reconcile the opposing results or figure out which study is more right or wrong.
And then for the seed, there's a study on rats that show it alleviates liver toxicity.
Overall, it's probably a food to avoid if you think plants and fruits are TRYINGGG TO KILLL L YAAAAA (>t. carnivores) but for normal people it is probably totally ok and even beneficial.
Even Ray misinterpreted the study according to what he says in his article: "Not all fruits, of course, are perfectly safe--avocados, for example, contain so much unsaturated fat that they can be carcinogenic and hepatotoxic."
When actually, the reference (the first study I mention showing that unrefined avocado oil tends to produce liver fibrosis in rats) in the article that Ray uses as justification for avocados being toxic due to their PUFA content, specifically says it is the non-fat portion of the avocado that causes the potential tendency for liver fibrosis, because the refined avocado oil with the non-fat portion removed produced no tendency for liver fibrosis. In the quote you can see from Ray above, he says avocados are toxic due to the PUFA content. I'v seen two studies, one being the specific one he mentioned, that show that his claim is completely incorrect and a wrong interpretation of the study to the extent I think he must have barely read the work he was citing.
Even the second study (Congolese women's breast milk fat content) he includes at the end of his article on vegetables says nothing really supporting his assertion that they are toxic, and I'm not sure why he bothered to include it.