The statement, “My assumption and my understanding is that if you are born of American parents, you are naturally a natural-born American citizen”, makes no statement whatsoever about the ‘natural born’ status of a person born of one citizen parent and one non citizen parent.
This statement, in regards to Obama, is meaningless.
My opinion, or yours, or anybody else's as to what the term ought to mean is irrelevant. The only issue is what an average well-educated voter reading the Constitution in 1783 would have thought the term meant.
Since the common law was the background for all legal terms of the time, the common law meaning should apply as the default. Under common law, native born = natural born.