That is a parroted fallacy disseminated by pathological debunkers (not calling you one) : Standards of Evidence should be consistent no matter what we are dealing with.
I think I should expand a bit on this reply.
The standard of evidence is greater for someone like Rossi and his E-Cat, as he has been shown to be a fraud many times.
Compare this with the other extreme of what we would ask for evidence about:
The sun coming up in the morning - we don't ask for strong evidence for that, as we already have lots of experience of it.
General relativity - proven in maths, and used in GPS applications. Attempts to disprove it are a sign of pseudoscience. We don't ask for strong evidence for GR or even SR anymore, although when it was first proposed, we did.
Nuclear fission - proven in maths, and in real world applications.
Nuclear fusion - proven in maths, and being developed. Progress has been made, and a road map set out which is being followed. Actual confinement was achieved for 30s in a Tokamak, and the US generated more energy than they put in, in an experiment in 2014. These are things that have been demonstrated beyond reasonable doubt, and we do not require extraordinary evidence, as the evidence is there. It is not hidden. They are scrutinised by other scientists, peer review occurs by some of the brightest people around, and the conclusions are published in journals. The whole process is not without its safe guards, although no system is perfect, they are not going to invest billions without these systems in place.
If the fusion facility at Culham suddenly announced it had achieved results far greater than what other experts were expecting they would want to analyse the experiment very closely, and the peer review would be very vigorous. It would have to stand up to that scrutiny, as there could be factors that weren't taken into account
With cold fusion, the maths have been shown it to be impractical, with confirming it to be a non-starter. The original experiment by Fleischmann–Pons has not been found to be replicable. Some experiments gave false positives, and a great deal of money was spent by universities and research centres looking into it, and none came up with a replicable system.
For it to work, it would have to violate well established physics. It is 2015, and these things have been well established through maths and experimentation for many decades.
So for a serial scammer to claim he has built a cold fusion device that provides cheap energy, you would need some extraordinary evidence, such as replicable results, analysis by independent scientists (this hasn't happened before you claim otherwise), in other words: peer review.
We should not and cannot accept the word of a serial con artist when we hold the rest of science up to higher standards.
