They went into vitamin B12 deficiencies in great depth, but all Wilks succeeded in doing is proving that you should eat grass fed meat, not grain fed and supplemented meat, or take a B12 supplement irrespective of your diet. He completely ignored the clear evidence of consistent and significant vitamin B12 deficiencies in vegans.
There was a good frrakonomics podcast called "how to change your mind". Seemed to say that on the whole, humans like to think that we look at evidence and make an informed decision on something. In reality that rarely happens, and we first form our views based on all sorts of complex biases, and then go hunting for evidence to support it afterwards.Well worth a listen.