Well he has a PHD in clinical psychology, not nutrition. I think people like the OP throw these jabs at him purely because they're angry he spoke out against the Canadian pronoun law, rather than any complaints about the validity of his research itself.

I think you’re right. But people have all sorts of crazy diets for unsupported reasons.

I don’t think Peterson is promoting the carnivore diet, but I did hear him explain his diet on a podcast and it seemed pretty couched in curiosity, not resolution. The thing I remember is lots of “I don’t knows” and attribution of any benefits to it being an elimination diet vs any special property of beef.

The meat only diet worked for his daughter(she has autoimmune disorder) and him apparently for whatever reason.

He also says its not a healthy diet in general and that he doesnt know if it will work for other people.

I think a lot of people try to twist his words(or assume the worst interpretation) even on "normal" topics because they dont like his Politics.

As someone who's mother died of a rare/poorly understood cancer after fighting it for 10 years and multiple experimental treatments, and met others in similar boats along the way (support groups), there are tons of niche medical conditions that science hasn't even bothered/had the resources to investigate.

Is a beef-only diet a good idea for the general population? Probably not. Could it be ideal for people with extremely rare auto-immune conditions that have an allergic reaction to virtually everything else? Sure, and that existing doesn't sound crazy to me at all.

I've noticed a trend where scientifically minded people tend to get hung up the "proven" at the expense of the "plausible", forgetting that everything they rightfully treat as proven once could have been dismissed in a similar manner. Real people in the real world have to make decisions based on nothing more than plausibility all the time, and I don't see why diet should be any different. Particularity if none of the "proven" solutions are working for you.

Put another way, there's a difference between "the evidence says this is wrong" and "there is no evidence that this is true".

Many autoimmune disorders react to food, for example the infamous Celiac disease is an autoimmune reaction to gluten, that is present in many cereals (not only wheat).

So why beef only wouldn't work?

I have autoimmune diseases myself and have a very meat heavy diet, to me is what works, as soon I move to a more typical diet my health declines quickly.

You can sarcastically toss out a list of uncontroversial useful or true things that have been said by literally anyone, no matter how often they’ve otherwise been wrong or harmful. It’s not a refutation.