"People in the past were wrong about what is possible, so clearly the naysayers are wrong about my thing!" See how stupid that logic looks? Trying to argue that cold fusion must be possible because people have been wrong about things in the past is arguing crosseyed badger spit. It is a nonsensical argument used by con men to deflect from their BS.
Here's the thing: With all these technologies that actually exist (#4 doesn't) you see two important things:
1) They are actually available to look at, in a non-controlled environment. You can verify them yourself, without some "researchers" standing over your shoulder, telling you what you can and can't see, what you can and can't touch. They are easy to verify they are real.
2) You can have the theoretical basis for how they operate explained to you, and that is consistent with our understanding of physics, chemistry, and so on. There's no hand waving, there's just science.
So when cold fusion hits that point, call me. When someone can say "Here is how this device works on an atomic/quantum level and why it is actually a fusion process," and when these claims are examined and confirmed by reputable labs at universities, where the researchers are given a device and allowed to do what they please with it, then I'm interested. Until then, STFU.