Excellent post. Two points I might add:
1. You note that not knowing how caffeine might cause harm doesn't stop scientists from concluding that it may. This is the same non-rational "science" that underlies many medications. Aspirin, Prozac, angioplasty, and many other meds and procedures have been routinely employed without any serious understanding of how they work.
2. This seems one area where an evolutionary perspective may be useful. It stands to reason that many of the substances/experiences encountered in the ancestral environment would be unthreatening to us, as we've had the opportunity to evolve defenses. In fact, many of the seemingly threatening substances have been shown to be beneficial (e.g., diseases caused by the lack of exposure to soil-borne pathogens). I suspect TV and caffeine are potent threats (real or not) because they did not exist until recently and so people instinctively suspect they may be vulnerable to them on some cellular level.

It's "oy gevalt", not "oy gevault." Geez.