I like the concept, but there's gotta be a better term out there:
If there's one thing I've learned in my years of delving into pseudoscience, quackery, and alternative medicine is that conspiracy theories are just like Lays potato chips; cranks can't eat just one. No, they have to stick their hand in the bag and pull out a huge, heaping handful and snarf it all down. Believers in "alternative medicine" quackery often also believe in New Age woo or other bizarre unscientific beliefs. Scratch a "9/11 Truther" and you'll often also find a Holocaust denier. One of my fellow ScienceBloggers, Mark Hoofnagle, has a great term for how cranks seem unable to be cranks in just one area, crank magnetism, complete with examples. Indeed, I've covered examples of just this phenomenon over the three and a half years this blog has been in existence.
Indeed, it would be hard for me to come up with a major 9-11 fruitcake who doesn't believe in some other batch of nuttiness as well. David Ray Griffin famously wrote a book about parapsychology (mediums, resurrection, remote viewing, etc.) before he went on to become the guru of the 9-11 "Truth" Movement. Steven Jones indulged himself in the Burrows Cave nonsense before he ever heard of thermite. Uncle Fetzer wrote three books about the JFK assassination, and another one about Paul Wellstone's plane crash.
Indeed, one time Rob Breakenridge asked me a question that I still kick myself for not getting right. He asked why the Troofers supported Ron Paul even though he'd specifically disassociated himself with the "Inside Job" theories. I should have noted that while he may disagree with them on controlled demolition at the WTC, he agrees with them on lots of their other conspiracy theories, like the North American Union, or the evils of the Federal Reserve.
Anyway, I like the concept, but somehow crank magnetism (coined by our buddy Mark Hoofnagle) doesn't cut it as a phrase. There's gotta be something better. The Unified Crank Theory? Conspiracy Theory Collectors? Or is there something terse that captures "If you're stupid enough to fall for x, you'll probably fall for y as well?"