I often wonder what these people get out of such interactions.
I think that, in many cases, it's essentially a cry for attention. "Please notice me! What I have to say is important!"
But to persist with posting the same debunked nonsense over a period of years or decades requires a special sort of immunity to listening to reason. I think that cranks like Tony probably start with good intentions, but quickly find that the subject matter that interests them is over their heads. Mostly, they lack any formal education in their pet subject - or else their education stopped at some point and they thought (wrongly, as it turned out) that they could make up the gap between what they were taught and what they wanted to investigate by themselves.
So, the crank invents a personal theory. He has a strong emotional connection to it, but lacks the ability to assess it objectively. So, he shops it around to some experts, who patiently explain to him what's wrong with it, why it's not fit for publication in the peer-reviewed literature, what additional work he would need to do to start to get it up to scratch (which would usually involve more formal education, which - for whatever reason - the crank left behind long ago).
The crank persists, thinking that sooner or later the odds are he'll find a receptive professional who is willing to spend a little time trying to help the crank. Sometimes this works for a while. An expert offers to help point in the crank in the direction of the additional work he needs to do. But in the end, it's all too hard for the crank, and the expert eventually realises this is a waste of his time and gives up on the crank.
Meanwhile, the crank is still shopping his revolutionary (flawed or useless) theory around the internet. Rejections and objections accumulate. After enough of them, the crank decides that the real problem is not his pet theory, but the scientific "establishment" at large. At this point, the crank turns into a conspiracy theorist and starts to believe that all science - or at least the science that tends to refute his pet theory - is dogma, and that professional scientists are either "sheeple" who follow the orthodoxy blindly or else are "in" on the Grand Conspiracy to suppress the crank's theory (which the crank now regards as indisputable Truth).
From this point on, the crank is stuck in a rut. He self-sabotages any hope for improving his own level of understanding of the relevant subject matter, since he now believes that the subject matter itself is "false dogma" that he needs to avoid. The best he can hope for is to drift around the interwebs, occasionally finding new people who are unfamiliar with the nonsense he has been shopping around for years. His currency is now the attention he gets for a short time, until he loses the respect of his latest batch of targets for his revolutionary, but sadly debunked and useless, theory.
Perhaps the saddest thing about the life choice of the dedicated crank is that, in all likelihood, the crank is good - or at least competent - at
something else. But he chooses to waste a not-insignificant portion of his life on trying to promote a dead "theory".
Actually, perhaps that's not the saddest thing. The saddest thing might be if the crank manages to convince another would-be crank to believe in the crank's theory and become a follower, in which case two lives might be wasted instead of just one. Possibly there is some good news: pseudoscientists often tend to be isolated. Even other cranks won't buy their theories, most of the time, if for no other reason than they are usually too busy with their own.
And let's not forget the emotional turmoil that must be a constant in the crank's life, as his pet theory is rejected time and again. On one level, he has to develop a very thick skin to keep at it after so much rejection. But I think that, most likely, deep down, there's sure to be a gradual diminishing of self-worth.
Do they imagine that they are perceived as intelligent, and the interactions therefore boost their egos?
I think for a short time, until the latest group of people notice that their credibility is minuscule, it probably does boost their ego. In the long term, though, crawling away with your tail between your legs for the n-th time has to take a toll, surely.
Do they crave any human contact, even negative contact?
I think the answer is probably: yes.
Do they honestly, actually believe their own woo and feel it is their "mission" to get the word out?
In the case of pet theories, I think they mostly honestly believe it. They develop protection mechanisms that prevent them from recognising why it's woo, or even seriously considering the idea that it might actually be woo. Remember, from their point of view, they are talking exclusively to sheeple or the Illuminati, in effect.
Is it a deeper dysfunction that makes them unable to NOT post, something like a written Tourette's?
When one is crying for attention, one wants to try to stay in the spotlight for as long as possible.
And one odd thing is that there are undoubtedly forums they could get onto and get all the attaboys they could possibly want. I mean, Tony here could just go on Truth Social and decry the liberal progressive relativity lie, and he would get all the positive comments he could ever want.
I'm not so sure. Each personal crank theory is idiosyncratic. I'm thinking mostly of the physics crank theories, here. There are many shared characteristics. Lots of cranks think they've disproved Einstein, for instance. But each one thinks he has disproved Einstein for different reasons, and two cranks are unlikely to agree that the other one's pet theory is the correct one.
More generally, of course, there are whole communities of cranks who are not really tied up in their own personal theories, but just like to join a community that distrusts perceived authorities and shares a certain political ideology.