There is an aspect to this topic that I almost never hear discussed, by "birthers" or others, that makes the argument even more stupid: namely, the definition of "natural born citizen." While the Constitution doesn't define it, and to my knowledge no statute specifically speaks to that exact phrase, the first rule of statutory construction is to look at the plain meaning of the text.
The phrase "natural born citizen" seems to mean anyone who is a citizen of the U.S at birth, that is, who was a citizen when he/she was "naturally born." (As opposed to, for example, someone who becomes a citizen later via the naturalization process.)
TITLE 8, CHAPTER 12, SUBCHAPTER III, Part I, § 1401 of the United States code defines "Nationals and citizens of United States at birth."
paragraph (a) : "a person born in the United States, and subject to the jurisdiction thereof."
Cool? If you are born in the U.S. (and not the child of a diplomat not subject to US jurisdiction), you are a citizen at birth. i.e. when you are "naturally born."
Skip a bunch of irrelevent paragraphs and we find paragraph (g): "a person born outside the geographical limits of the United States and its outlying possessions of parents one of whom is an alien, and the other a citizen of the United States who, prior to the birth of such person, was physically present in the United States or its outlying possessions for a period or periods totaling not less than five years, at least two of which were after attaining the age of fourteen years:..."
Right. So, let's just assume, for fun, that the birthers are correct, and Obama was born in Kenya. According to the biography of Ann Dunham, Obama's mother, which, as far as I know is not seriously contested, she was born Nov. 1942, in Kansas, moved around the midwest a bit during and after WWII and then to Seattle in 1956. When she graduated high scholl, in 1960, the family moved to Hawaii (which became a state in 1959.) There, she met and married Barack Obama Sr. She was 18. Let's do the math.
Obama's mom a citizen: Check. Born in Kansas.
Was physically present in US five years or more: Check.
Was physically present in the US at least two years after her 14th birthday: Check.
So, assuming she and Barack Sr. immediatly moved to Kenya, had a child, and then surreptitiously brought the child back to the U.S. and had someone forge a birth certificate, he was still, according to law, a US citizen when he was "naturally born," ergo, a "natural born citizen."
Of course, citizens born abroad get a "certification of birth abroad to a U.S. Citizen," rather than a certifcate indicating they were born in the U.S., but that's neither here nor there. Even if he was born in Kenya, Barack Obama Jr. is Constitutionally eligible to be President of the U.S.
Therefore, I respectfully request that the OP acknowledge the same unless he can produce evidence that Obama was born abroad, that his mother was not a U.S. citizen at the time of her birth, and/or that she was not physically present in the U.S. for the requisite time period prior to his birth.
(Full disclosure: I practiced immigration law for 7 1/2 years and guarentee you that a certified copy of a "Certifcate of Live Birth" issued by a State entity is considered proof of one having been born in the United States.)