Of course there isn't one! It is bullshiite like this that absolutely invalidates the quest to determine eligibility. How damn many ways are there, exactly, to tap dance around the central fact of the issue?
That is, the man's father was a foreigner. That is the beginning and the end of the eligibility story.
The real questions are,
(1) "Who is paying for the constant recycling of this mis-and dis-information?"
(2)"Why is it that NO LEGAL AUTHORITY that has the power to do do something about eligibility, has not done so? Even worse, why have they categorically refused to fulfill their sworn duties?"
Unfortunately, that is merely your opinion. Not a fact.
If that definition of a "natural-born citizen" was widely shared, somebody would've raised their hand and broached a question months before the 2008 election. Nobody did.
Ipso facto, almost all jurists, legal minds and political animals hold a contrary opinion.
Who's right? I don't know. And neither do you, though you're entitled to your opinion. And you are absolutely right -- the eligibility question absolutely must be addressed and firmly resolved...forever.