"[I] find no fault with the introductory clause [S 61 Bill], which is simply declaratory of what is written in the Constitution, that every human being born within the jurisdiction of the United States of parents not owing allegiance to any foreign sovereignty is, in the language of your Constitution itself, a natural born citizen...[6]"
However, what Senator Bingham said in his very next sentence does not support the author's interpretation, and I find it very telling that he did not include it. He continued: (the words below follow immediately after the above quotation, with no intervening words.
... but sir, I may be allowed to say further, that I deny that the Congress of the United States ever had the power or color of power to say that any man born within the jurisdiction of the United States not owing a foreign allegiance, is not and shall not be a citizen of the United States. Citizenship is his birthright, and neither the Congress nor the States can justly or lawfully take it from him."
Note it is the man himself, and not his parents that the good Senator referred to as "not owing a foreign allegiance".
That statement by the man the author says is "considered the father of the Fourteenth Amendment", kind of throws the author's argument right into a cocked hat, doesn't it? You can check it out at: The Library of Congress. You'll have to manually put in the page number, 1291, as indicated by footnote [6] in the original article.
BTW, the good Senator was not speaking on the resolution that would become the 14th amendment, but rather on a civil rights bill. Later in the transcript we see him arguing that Congress did not then, prior to the 14th amendment, have the power to forbid discrimination by the states on account of race by a passing a mere law. He argued for a Constitutional amendment. Later that year, the resolution that would become the 14th amendment after ratification by the states passed both Houses of Congress by very lopsided votes.