You are correct about nutrients, to a degree, but I'm also not saying eat nothing but red meat. Theres essential nutrients in meat/animal products as well that you cant easily get from vegetables/vegan diet...Omega 3's, B12, and easily usable iron for example, all of which are crucial to performance and health.
I don't know if it's true or not, but I've read/heard somewhere that if you don't eat red meat for a while, then eat it, it can really do a number on your bowels.