"If Merrick was still alive and producing and treating his staff like shit on the order of what Rudin is accused of, I'd be all in favor of him going away too."
I agree with you in spirit, but I guess the salient point here is that psychological abuse is abhorrent but not necessarily actionable from a legal standpoint, whereas physical attacks are. (I am not aware of any stories of physical abuse on Merrick's part, but maybe there are such stories and I just haven't heard them.)
I once had the great displeasure of working for someone who, among her other major failings as a boss, made outrageously inappropriate comments about the personal lives of some of her employees. As abhorrent as her behavior was, I suppose it would have been difficult to claim that any of it was actually illegal. Of course, in situations like that, HR departments can and should be helpful -- but we didn't have one, so that wasn't an option for me.