Why did African Americans go through such struggle, according to "the Negro Mother"?

Langston's Hughes's poem is narrated by "the Negro Mother," who is representative of black people's maternal ancestors.
Her story begins during her kidnapping in West Africa ("I am the child they stole from the sand / three hundred years ago in Africa's land"), continues to her perilous journey across the Atlantic, while pregnant, as part of the first generation to become slaves in the Americas ("I am the dark girl who crossed the wide sea / Carrying in my body the seed of the free"), and her years of indignity as a slave:

I am the woman who worked in the fieldBringing the cotton and the corn to yield.I am the one who labored as a slave,Beaten and mistreated for the work I gave — Children sold away from me, husband sold, too.No safety, no love, no respect was I due.

Her life was further marred by illiteracy and indifference, but it was her hope for the next generation, as well as her insistence on understanding history as memory and heritage, that kept her "trudging on through the lonely years."
Black women, represented by "the Negro Mother," struggled due to state-sanctioned racism, which turned black bodies into property. Though all women have historically experienced sexism, the black woman was not offered the protection or respect typically given to white women. She was not given the respect typically shown to wives and mothers, nor allowed discretion or privacy over her own body, due to the routine exploitation of black women.