Absolutely not true. If Mitt had been an American Indian born in Detroit in 1920, he would NOT be even a citizen, let alone a "natural born citizen." Place of birth is but one requirement to be a "natural citizen." Anchor babies are NOT "natural citizens."
Anchor baby is not applicable in Obama’s case because we deported his father back to Kenya. Unfortunately, he left his Kenyan son here because he had dual citizenship. We failed to deport the whole family.