Why did the U.S. refuse to accept Elizabeth Cady-Stanton's argument to abolish gender discrimination?

Abstract

Born to a wealthy family in 1815, Elizabeth Cady Stanton changed dramatically a number
of social and political elements of the US. She was one of most influential early activists of the US woman's movement. The most important point in her career was her Declaration of Sentiments. This significant event in the history of women's rights in the US, made her the founding figure of the movement. For the first time, a document in favour of improving women's rights had been signed by 100 activists. (http://www.nytimes.com/learning/general/onthisday/bday/1112.html).

Her social activism cover a wide range of topics within the issues of time experienced by the women of the time, including their right to vote, contraception and birth control, regulation on marriage and divorce, and many other concerns (Baker, 2005). After the Civil War, Stanton opposed the implementation of the Fourteenth and Fifteenth Amendments to the U.S. Constitution. The reasons for this opposition were the situation of inequality that these amendments supposed. In her view, the amendments supported and reinforced that inequality of women with respect to men, as they would provide a wide range of regulations to legally protect African American men, as well as providing them with the right to vote, while on the other hand, the rights of African American females would remain the same, as they would still be denied the right to vote, like their Caucasian counterparts.