I think the physics "theories" come from a desire to see that scientists are wrong. Some people seem really attached to the idea that scientists are lying to them or that current scientific knowledge is easily disproven.
Sad folk they be.
I think there's an anti-intellectual undercurrent in general - the idea that formal education is a sham and anyone who has a serious degree is in on it, perpetuating the lies. When you see an interview with a pseudoscientist, check out their credentials: it tends to be something like expert on Ufology, many years of research work, a document hoarder's living room, and an AA in a social science from the University of Santa Cruz. Frequently you'll see no formal degree at all, but a certificate in eastern medicine or spiritual energy or something.
Chiropractors in the US must complete a very short Masters-equivalent tech school experience and that's it before being allowed to practice; conversely a medical doctor goes through double the schooling, long internships and residency, and consequently will acquire skills commensurate with calling him a "doctor". Of course the American Chiropractic Association website makes it sound like chiropractors are even more skilled and knowledgeable than medical doctors - again with the "we know better than the professionals."
This "get one over on the experts" is part of the fuel for the diet books that claim to know the real answers, homeopathic remedies that can't possibly do anything at all, and unregulated herbal supplements that could actually do some harm. It's inconceivable to these people that if something actually worked well, real medical professionals would adopt the practice or medicine and it wouldn't be on the fringe anymore.
Some of this mistrust is virtually ancestral, like lawyer-hatred and expecting the mechanic to screw you, and probably stems from being in a bad situation and needing professional help but finding that the whole experience is going to cost a lot of money. Rather than the very sensible approach to this expense, to learn from your mistakes and avoid the harm in the future, and to understand that sometimes a thing will happen to you that is bad and costs money, the pseudoscientist mindset says, "they're all just trying to rip me off, I can probably fix this just fine by peeing on a turtle or rubbing dirt on it."
Some of the mistrust comes from a professional telling you that there is no alternative. Desperation. If a doctor says your cancer is terminal, you might just start eating all the fruit to see if the whacko you found on late-night public access really has found a cure for cancer. It's a sailor's superstition, trying everything because you lack control of your situation and latching on to anything that correlated to any improvement.
There's also a mistrust of any large organizations and a preference for a smaller, grassroots approach to anything regardless of the values and history of the organization. Almost an "if I didn't bake it myself, the cookie is probably poisoned" attitude. Again, this speaks to a desire for control of one's situation even if that control doesn't result in better outcomes.
Then there's the fortune-teller's fallacy where you remember all of your "hits" and forget your "misses". If you take ginkgo for memory and energy, you're going to remember that one time when you did really great stuff right after taking it - forgetting all the times it didn't help at all. And that's ignoring your placebo effect where peeing on a turtle can improve whatever you believe it might improve, which isn't an indictment of medicine so much as it is a testament to humans' ability to fool ourselves.
There is also a credulity in pseudoscience, a failure to validate your sources. But when the pseudoscientist is himself not a great source, and mistrusts authorities, it makes sense why he references writers like Von Daniken et. al. But part of it is an issue present in anyone doing research: you can't start with your conclusion and then gather all the evidence that supports you. You'll never learn anything and you'll frequently be wrong! Instead you research everything and from that material draw your conclusions, which may be totally opposite what you expected in the first place.
The last thing I can think of is a sense of punking the establishment, of making others appear foolish and the pseudoscientist appear superior and triumphant. But that's present in a lot of different people, and especially real scientists. In fact I think that's one of the core values that drive science.