Actually, there's debate as to whether or not bearded dragons should eat pinkies, not to mention larger live food. Generally, I believe that if they can get along just fine with safe, staple insects, and live perfectly healthy lives, I don't see any point in feeding anything larger (can cause impactions), fattier (can result in fatty liver disease), and/or bonier (can cause internal injuries).
As for the topic, I have heard and have seen bearded dragons eating other lizards. I just would never recommend anyone actually intentionally feeding a lizard to a bearded dragon.