In horseback riding combat, the horse needs to be strong, not the rider. The idea that diet played a role in this and not geo-politics and military tactics is a bit out there.

Red meat being tied to masculinity is big right now (Rogan, Alex Jones, alt-right, etc) and its sad that shoddy arguments are being made like this to keep people from mindfully considering what exactly it means to raise and slaughter all these animals, some of whom are empathic and social mammals just like us. Worse, meat consumption is tied directly to cancer and heart disease. You're not going to be "strong" on chemo and its not "strong" to be dead a decade or two or three before you should because of your poor diet. Not to mention the link to obesity, that often starts in childhood, so a lifetime of being obese also isn't "strong."