None of the research quoted is about people deliberately eating only meat/animal foods trying to improve their health, and it's mainly just correlation studies that can show people who eat more meat (when they believe it's not healthy because Dr. or government chart says so) likely don't care about their health much. And they keep talking about "inflammatory" foods. Yes, I think that is a problem for depression and eliminating those foods could be highly beneficial. But meat isn't one of them. Meat tends to be one of the very low inflammation foods.
Increased meat and sugar? Yeah, that'll cause some problems because they've lumped in sugar with the meat. Washing down that meat in the big bun with a coke? Yeah that kind of high meat consumption is a problem. Not the same as an all meat diet at all. Can't predict the results of one from the other.