Extraordinary evidence

Over the past few years I've been almost pessimistic about some phenomena - let me explain, before I'm dismissed out-of-hand as a "scofftic" or something. I've begun to ask myself what sort of evidence would really be necessary to prove things. For example, take the UFO mystery - or actually, say something less nebulous, like the identity of Jack The Ripper. Say through some discussion or discovery of long-lost files or something, you find out, 100%, beyond a shadow of a doubt, who Jack was. What would it take to convince others? We could come out with proof, explain succinctly the identity and provide the original files, maybe, to back us up. But look at it from someone else's point of view: no matter your evidence, there's a certain number of folk in whatever mystery field that will always view it as nothing more than yet another theory. Even if indisputable evidence were provided, people would say that you hoaxed it, or misinterpreted something... regardless of what happens, there's a subset of the populace who want it to stay a mystery forever. Although I used the Jack example, obviously this same logic follows through for Bigfoot, UFOs, eastern pumas, the Loch Ness Monster, ESP, the Great Siberian Explosion, or what have you.