I dunno, it could also be someone who thinks they're just being loyal to the emperor. His butthurt, as you say, was so obvious it might have been too obvious. Everyone and their mother already knows the Feng family was perhaps acting a bit "out of line" as it were towards the emperor recently. Actually, not bad timing for someone who just has a grudge against the emperor to make a move either. He's the obvious suspect and all, maybe take down a rival in the process of making the emperor look bad.