http://www.ufoevidence.org/documents/doc927.htm
Let me give you an example of what I mean. Let's imagine that I said to you 
"UFOs are created by an omnipotent source of energy which can create 
whatever it wants to. We can't reject any UFO-oriented accounts, because, no 
matter how absurd or inconsistent they seem, since we're talking about an 
omnipotent force, it can do anything". This must be ultimately 
unsatisfactory, because it doesn't help us focus on the problem and weed out 
the useless chaff. In fact, it is counterproductive, because it makes us 
weaken the filter to a point where one must draw conclusions from material 
which would be, and should be, rejected in any other field of science. Such 
are the consequences of the paranormal theory.