Because according to Article II's most usual historical interpretation, in order to be a "Natural Born Citizen," both one's parents have to be citizens at the time of the candidate's birth.
If this interpretation of the Constitution has been incorrect, it is up to the courts to tell us so, or the Congress may amend the Constitution to make it so. It cannot be settled in freeper dialogs.
BTW, Reich is a hardened Democrat Partisan Worker. It just may be that he has been assigned the task of deflecting Obama's issues with eligibility. That is, the Democrat Party's wish to make Obama the precedent for equating "Native Born," with "Natural Born." (In Obama's case he has been unable to definitively prove that he is "Native Born," and of course, cannot possibly demonstrate that both his claimed parents were citizens at the time of his birth.)
The Team Obama PR effort has been in full swing since 2006 and has actually worked quite well for them so far. They have been able to re-direct public attention to the alleged place of birth, rather than the circumstances that govern constitutional eligibility.
In my research I found NO indication of the requirement to which you write.
“Because according to Article II’s most usual historical interpretation, in order to be a “Natural Born Citizen,” both one’s parents have to be citizens at the time of the candidate’s birth.”
Were eighter, especially the father, a U.S. Citizen when Rubio was born?