Care to name who you're talking about?  There's not much that can be done either way, but someone might be able to call his attention to this thread and perhaps he can address it here--but I suspect you don't want to call attention to yourself. 

I'd say just move on and find another bounty.  The threat of negative feedback was probably an empty one anyway, and most bounty managers, to my knowledge, don't make false accusations so as to deny payment and/or blacklist members.  Either way, I'd be interested to hear his side of the story.