And I strongly disagree with the reasoning stated above.
I don't disagree one bit. I will never vote for a woman president. Never. Ever.
FMCDH(BITS)
That is certainly your right. As it is your right to refuse to vote for someone on the basis or race, ethnicity, or any of the characteristics of one's birth.
But you might want to bear in mind that gender did not seem to be an impediment to Margaret Thatcher's performance in the UK in the 1980s.
Of course, Hillary is no Margaret Thatcher. I oppose Hillary because (1) she is a closet leftist, who vacillates between making centrist noises (for general-election purposes) and trying to mollify the leftist base of her chosen party; and (2) she is plainly Machiavellian--which is to say, principle-free--but for more on this, see the previous point.
But if you sincerely believe that all women are, by definition, unfit to serve as president, then we will just have to agree to disagree.