Here's a must read for any low-carb health enthusiasts: a transcribed conversation between gurus Dr. Mark Hyman and Chris Kresser, discussing what constitutes a healthy diet.
What is their conclusion? That you'll get a long way with common sense, that butter could be a part of a healthy diet and that there's no reason to fear red meat.
Heleo: Why Fat, Butter, and Red Meat May Be Just What the Doctor Ordered