Sexism in the campaign

If a male says he doesn't want Senator Clinton to be president, because he, or the country, is not ready for a woman president, that is generally considered to be a bad sexist attitude. If a male says he is againt Clinton for some other reason, there seems to be a presumption by some that he is simply a closet sexist.

If a female says she wants Senator Clinton to become president because it's time that we had a female president, is that sexist? If not, why not?

I resent being told that the reasons I give for preferring other candidates to Clinton are simply masks to hide my secret desire to continue the White House as a male-dominated institution. There are other good and valid reasons to think that Clinton is not our best choice for president.