I divide conspiracy theorists roughly into three categories (in order of severity):
Firstly, there are just your everyday people who happen to believe in one of more conspiracy theories, but don't stress too much about it. They might even never talk about it unprompted. They are simply being naive and deluded because they lack the experience and healthy skepticism to catch the argumentative errors in your typical conspiracy theory, and they happen to find the idea enticing.
Secondly, there are the fanatics. These are the people to whom conspiracy theories are a religion (not a theistic religion, but a religion nevertheless.) They cannot stop talking about it, they have to constantly proselytize to others about it, and they are overall quite obsessed about it. I saw a video of a former conspiracy theorist of this type where he described what it was like, and what kind of effect it had on his life. He became "converted" after someone handed him a DVD containing the pseudodocumentary Loose Change, and afterward he became literally obsessed with the subject. He became extremely passionate about it and couldn't stop talking about it, and at one point it became so bad that his girlfriend left him because of it. It was, basically, his entire life. (He later came to his senses and started thinking more rationally about it and applied healthy skepticism, and consequently "deconverted".)
And then there are the third kind of conspiracy theorist...
You might ask how it can be even worse than the second type above, but let me assure you, it can.
The obsessed theorists described above are at least mentally sane in that there's nothing inherently wrong inside their heads. They have simply been deluded and become obsessed. The third type, however... is just like watching into the depths of pure madness.
Picture in your head a small dark room with just a slide projector on, and a guy wandering in and out of the light beam, as the projector beams random images onto a wall, and the guy rambling and rambling mostly incoherent random things, jumping from slide to slide with little to no structure. The tone of voice is mostly smug and full of itself, sometimes even chuckling. The content of his speech has little to do with actual reality and mostly to do with some kind of imaginary world that he has concocted inside his head, a world that completely dismisses even the must mundane facts of physics and jumps to the wildest of conclusions without any kind of rationality. The claims are outlandish even by conspiracy theory standards, and are presented completely seriously.
Well, you don't have to solely picture that scenario, because you can find such videos on Youtube and elsewhere. These videos often feel like strange performances of abstract art... except that it's quite probable that the people in the videos are actually being serious and believe everything they are saying. It's difficult to describe in words the feeling one gets from these videos, but the demeanor and behavior, alongside the setting and the words, and the tone and manner of speaking, give a really strong impression that's almost scary to look at. It's like looking directly into pure madness.
There's something seriously wrong inside the heads of these people, and I really think they should seek professional help.