I think one of the biggest confounders in the discussions, and the reason people keep talking past each other, is there not considering the metabolic context of a carnivore diet.
A pizza with a little meat on it, is mostly sugar, via carbohydrates. And seed oil.
A fast food meal, is mostly carbohydrates, buns, oils, soda, and a little bit of beef.
These two example meals are really unhealthy, the meat is not what's making it unhealthy
If the basis for your epidemiological cohort considers red meat eaters the people eating pizza and fast food, and not the people doing zero carb carnivore. Everything is going to look bad. Because all of that sugar is really bad