Check out this essay by Jack Woodall in The Scientist:
Intelligent Design: The Clincher — A butterfly explodes the theory
Follow Woodall’s argumentation to its inevitable implications:
If I were the perfect designer I would invent a perfect world in which nothing could possibly ever go wrong or present any challenges or adversity. But then my world would be hideously boring and meaningless (and there would be nothing to learn, because learning takes effort, and effort means challenge and adversity), so I would no longer be the perfect designer of a perfect world.
I couldn’t win for losing, and in either case (a “perfect” world or an “imperfect” world) my design would be imperfect, and therefore would not be designed.