I’m going to be honest, I feel that these ideas do not come from a place of science but from a political bent that meat is bad and therefore we should eat less of it. This is inconvenient because it does not fit actual facts of reality (humans work best with an a meat based diet but can in a pinch eat just about anything) and therefore reality must be denied. Those who point out that what they say is wrong will get the usual treatment for that.
I admit this is conspiratorical.