The quote "Let southern oppressors tremble, I shall strenously contend for immediate enfranchisement" was from a speech given by Frederick Douglass in 1865. In this speech, Douglass called for the immediate enfranchisement of all African Americans, and warned that those who opposed this would face the wrath of the newly freed slaves. Douglass argued that African Americans had earned the right to vote through their service in the Civil War, and that their enfranchisement was essential to the future of the United States. This quote is a powerful reminder of the struggle for civil rights in the United States, and of the important role that African Americans have played in shaping the country.