If he finds someone that is willing to invest in his project, let it happen, and when the cold fusion device turns out to be a scam, let them report it to the police and trow him back in jail where he belongs. The best way to deal with a bluff is to call it, not argue about it.
The problem is that people like this undermine the public trust in science. That is a huge problem because it opens the door to allow an entire other set of charlatans into the picture. These other people gain traction only because the name of science has been tarnished as the provider of truth. Once this other group of people have the public ear, they start pushing all kinds of counter productive BS like creationism and other idiot dogma
Our governments need to assign science and all its keywords as trademarks to a standards body and give them full right to enforce. This will help to put an end to all of those deceitful commercials that begin with "scientifically proven to xxx". Joe Sixpack doesn't even understand how they're being lied to, or even that they are, and that failure to understand is in no small part due to the behavior of people like Rossi and his associates.