At least for your craigslist example, the fear is not unfounded. [0] That one example happened just last month in my town. The weapon in that case need not be a gun, a knife or baseball bat wielding friend hiding in the bushes would work well too. Perhaps better than Starbucks would be the police department parking lot. That is actually a preferred place for private gun sales - if the buyer is uneasy about conducting the sale at a police station, they are probably a person prohibited from owning a firearm. Our town has added a designated "craigslist zone" at a local fire department precisely to help deter robberies. [1]
So, in the craigslist example, many American people are afraid because there is overwhelming evidence that craigslist robberies A) really do happen with some significant frequency and B) meeting at a public place is a simple, low-effort way of mitigating that risk. I can understand people living in lower crime areas not worrying about craigslist robberies (though I would take the precautions anywhere because it is so simple).
However, in general, I would agree with you that Americans eat up FUD. You can see it in our DHS/TSA, the Patriot Act, collective disinterest in the Snowden leaks, and general anti-Muslim sentiments.
[0]: http://wlfi.com/2015/08/18/man-robbed-at-gunpoint-while-meet...
[1]: http://wlfi.com/2015/08/18/lafayette-adds-monitored-exchange...
