I appreciated the emphasis on achieving nutrient density and balance in the diet and perhaps supplementing when necessary.
My genetic testing revealed, that I am one of those people mentioned in the presentation (A379V + R267S), who are not very efficient at converting beta-carotene to vitamin A. With my particular genetic constellation, that's about a 69% reduced capacity. I take cod liver oil, because despite following a balanced diet, I can not even come close to the RDA of vitamin A. I eat liver and actually crave it from time to time. Luckily, it never occurred to me to become a vegan, maybe I knew intuitively, that this would not be good for me. With my genes, that would have been a great way to ruin my health.
I was impressed with how Chris Masterjohn handled the question about how to get vitamin A within a vegan framework. While I am not a vegan myself, I respect someone who made the decision to not eat flesh for ethical reasons. As Chris Masterjohn pointed out, some people's genetics may enable them to be vegans without causing health problems. Vegans who do have health problems are not going to be helped by antagonizing them but will have to be educated and helped to find alternatives, and if the alternatives fail, perhaps they can take that daily spoon full of cod liver oil.