Which sentence in this excerpt from "Reconstruction" by Frederick Douglass best expresses the central idea?

The assembling of the Second Session of the Thirty-ninth Congress may very properly be made the occasion of a few earnest words on the already much-worn topic of reconstruction.

Seldom has any legislative body been the subject of a solicitude more intense, or of aspirations more sincere and ardent. There are the best of reasons for this profound interest. Questions of vast moment, left undecided by the last session of Congress, must be manfully grappled with by this. No political skirmishing will avail. The occasion demands statesmanship.

Whether the tremendous war so heroically fought and so victoriously ended shall pass into history a miserable failure, barren of permanent results,—a scandalous and shocking waste of blood and treasure,—a strife for empire, as Earl Russell characterized it, of no value to liberty or civilization,—an attempt to re-establish a Union by force, which must be the merest mockery of a Union,—an effort to bring under Federal authority States into which no loyal man from the North may safely enter, and to bring men into the national councils who deliberate and vote venomously, and who do not even conceal their hate of the country that conquered them; or whether, on the other hand, we shall, as the rightful reward of victory over treason, have a solid nation, entirely delivered from all contradictions and social antagonisms, based upon loyalty, liberty, and equality, must be determined one way or the other by the present session of Congress. The last session really did nothing which can be considered final as to these questions. The Civil Rights Bill and the Freedmen's Bureau Bill and the proposed constitutional amendments, with the amendment already adopted and recognized as the law of the land, do not reach the difficulty, and cannot, unless the whole structure of the government is changed from a government by States to something like a despotic central government, with power to control even the municipal regulations of States, and to make them conform to its own despotic will. While there remains such an idea as the right of each State to control its own local affairs,—an idea, by the way, more deeply rooted in the minds of men of all sections of the country than perhaps any one other political idea,—no general assertion of human rights can be of any practical value. To change the character of the government at this point is neither possible nor desirable. All that is necessary to be done is to make the government consistent with itself, and render the rights of the States compatible with the sacred rights of human nature.