The quotation from "Ain't I a Woman" by Sojourner Truth supports the central idea of the speech that women are just as capable and deserving of rights and respect as men. By asking where Christ came from and answering that he came from God and a woman, Truth is pointing out the importance and value of women in society. She argues that if women played such an essential role in bringing forth the son of God, then they deserve to be treated with the same respect and dignity as men. The quotation challenges the idea that men are superior to women and asserts that women are just as vital and valuable to society.