If one gets a citizenship through parentage, as Barack Obama received at birth a British citizenship, it would bring into question for him being a natural born citizen. His allegiance would be partly to the United States, if was born in Hawaii, but Obama would also have an allegiance to England. His allegiances would be split that the founders wanted to avoid for the president of the United States.
The United States fought two war with the English empire to break away from them and their laws. The War of 1812 was partially fought over the British Empire because the British were taking US citizens and forcing them to serve in the English navy because they believed "once a British subject always a British subject." You don't fight a war or two over citizenship and then turn around and leave the question open to having a president of the United States under the allegiance and jurisdiction of another country. The US Constitutional is not the Blackstone Commentaries or common English law. On the contrary, the US Constitution became US common law and not English law.
Whatever the semantic or original intent of the Founders was at the time of the framing of the Constitution, that gives way to the judicial findings of the Supreme Court. This is the nature of Constitutional Law. While one hopes that Supreme Court jurists would give deference to original intent, as a practical matter of law, it not what they should do or should have done, but what they have done that matters.
What they have done with respect to "natural born citizen", and who is or is not one, is clear. If Obama was born in HI, he is a "natural-born citizen" as that phrase is interpreted today, irrespective if that is counter to original intent.
This is Donofrio's shortcoming. He want to get into a a debate about what the founders intended, and ignore what the Supreme Court has actually done over the years. A competent constitutional lawyer (one who has a history of success at the appellate level) wouldn't make such an amateur mistake.