Wasn't it excessive rudder inputs that brought down the AA Airbus over Queens, NY in October 2001?
Methinks your employer has a potentially very serious problem on their hands with this cowboy; and if they (or their representative) have shown unwillingness to take the appropriate action in preventing a serious incident or worse, then perhaps somebody should be sidestepping the regular chain of command and going straight to the top. Failing that there's always the possibility of a confidential report to the relevant Regulator.
I certainly wouldn't like to have it on my conscience if something were to happen and know that a catastrophe could've been prevented if only I'd passed on the info to the right person in a timely fashion!