Why do we fear Alberto anyway?

So today I was babysitting my little cousins and like so many other kids across the United States, they get a bedtime story before they go to bed.  Tonights pick was a story called "Alberto the Dancing Alligator."  The story chronicles the fun times shared between a young girl and her alligator until one day the alligator is unfortunately, accidentally flushed down the toilet.  Madness ensues as the poor lonely Alberto begins to pop his head up out of random toilets, looking for his young owner, in the process frightening many people who consequently call the police.  Then another story emerges; the classic story of how one event is exaggerated until an entire community is convinced there are a thousand alligators roaming the sewage system.

It's not always alligators, sometimes it's skull caves and schools as in "Pooh's Grand Adventure: Search for Christopher Robin."  Christopher writes that he must leave for "school" which Pooh (not being able to read) interprets as "skull."  This misunderstanding leads the clan on an adventure through the scary skull territories, which upon leaving they realize aren't really that scary or big or intimidating.

As a society we have a very strong fear in the unknown, which apparently could have come from a childhood filled with books just like these.  Some could even say that fear is part of what starts wars, as in our war with Iraq.  I would argue that that war was partially started out of fear.  Fear that Iraq had nuclear weapons, fear that we didn't know what they were capable of, and fear of a problem that we didn't completely understand.  All we really knew was what the media let us know and that created a very rooted fear within the United States.  Why do we always fear the unknown, instead of just trying to find out what is really there?