Something you seem to fail to understand is that it is possible for people to be called wrong without also being deluded or liars. I have never called people liars, nor are they deluded. But you should recognise that the human senses are inherently untrustworthy. I've lost count of how many times I've fallen tens of metres in my bed while going precisely nowhere, for example (hypnic jerk), while study after study exposes the fact that eyewitness evidence is unreliable, for example by being led to see what the questioner wants to see, or misinterprets what was seen. And these are just some of the reasons for being sceptical of ghost stories, or dowsing, or whatever. You should be sceptical of your own senses -- and in fact it is arrogant not to do so, not to recognise that your own senses are untrustworthy, unless you go to great lengths to ensure otherwise.
I never called anyone a liar or a fraud. They were just (almost certainly) wrong. Most likely not wrong about what they saw, but wrong at least about how they interpreted it. It's not rude to say that. But are you arrogant enough to think that you are the only person capable of observing the world properly? Are you arrogant enough to think that thousands upon thousands of scientists whose job it is both to do so, and to try and ensure that they account for all possible sources of error, have not considered the idea that they might be wrong, that is so blindingly obvious to you? And finally, are you arrogant enough to believe that only you, or rather only through your own method of "rational study" are capable of certainty?
I would like to think that the answer to all these questions is "no". But in order for them to be "no", you need, like I said, to recognise that the human experience is subject to all sorts of flaws, and that your own senses are just as unreliable as anyone else's. Yes, including mine. Not to recognise this basic truth would be most arrogant indeed.