A difficult theory.

Really, it is.
Confusing. Hard to grip the mind around.
People are very often afraid of what they don't know. Scared of the unknown, simply enough.
But other times, if they can't see it, they are completely comfortable.
There are these two or three dogs that live in a house just up the street from where I live. Very few people in the neighborhood liked them. They used to be enclosed in a small, rickety brown fence. Which they broke once. They gate hung loose and we saw the dogs in our backyard.
Recently, I believe more people have been complaining. Our mailbox is set right in front of the yard of said house, and my mom never liked stopping there if the dogs were outside because they're 'vicious.'
The owners have just put up a high, sturdy-looking, tight white fence.
No more problems.
The dogs are still there, but no one is annoyed any more.
See?
They aren't afraid, just so long as there's nothing frightening to look at.