The crucial difference is that the mRNA virus, when finally scrutinized, was shown to be effective with effects that could be consistently replicated and there

The crucial difference is that the mRNA virus, when finally scrutinized, was shown to be effective with effects that could be consistently replicated and there was a theoretical explanation consistent with other things we've observed about mammalian immune systems. People were absolutely correct to dismiss the claims about the mRNA virus until those demonstrations were available, and would be wrong to dismiss them afterward. Cold 'fusion' is still in the first phase and has been for decades. Science isn't about what might be right. It's about what can be demonstrated.