Well, why not begin with people that actually agreed with his quotes as you present them:
During the Lincoln-Douglas debates the year before Stephens' speech, Abraham Lincoln had said this: ". . . anything that argues me into . . . [the] idea of perfect social and political equality with the negro is but a specious and fantastic arrangement of words, by which a man can prove a horse chestnut to be a chestnut horse. . . .
“I have no purpose to introduce political and social equality between the white and black races. There is a physical difference between the two, which in my judgment will probably forever forbid their living together upon the footing of perfect equality, and inasmuch as it becomes a necessity that there must be a difference, I, as well as Judge Douglas, am in favor of the race to which I belong, having the superior position."
In another speech later that year, he said: "I will say, then, that I am not nor ever have been in favor of bringing about in any way, the social and political equality of the white and black races; that I am not nor ever have been in favor of making voters of the free negroes, or jurors, or qualifying them to hold office, or having them to marry white people. I will say in addition, that there is a physical difference between the white and black races, which, I suppose, will forever forbid the two races living together upon terms of social and political equality, and inasmuch as they cannot so live, that while they do remain together, there must be the position of superior and inferior, that I as much as any other man am in favor of the superior position being assigned to the white man."
The following are excerpts from a speech given in New York by a politician addressing the Union Meeting on December 19, 1859: “As a white nation, we made our Constitution and laws, vesting all political rights in that race. They, and they alone, constituted, in every political sense, the American people.
“As to the negro, why, we allowed him to live under the shadow and protection of our laws. We gave him, as we were bound to, protection against wrong and outrage but we denied to him political rights, or the power to govern. “
"We left him in the condition of a bondman. Now, gentlemen, to that condition the negro is assigned by nature."
“Experience shows that his race cannot prosper—that they become extinct in any cold, or in any very temperate clime; but in the warm, his race can be perpetuated, and with proper guardianship, may prosper.
“He has ample strength, and is competent to labor, but nature denies to him either the intellect to govern or the willingness to work. Both were denied him.
“That same power which deprived him of the will to labor, gave him, in our country, as a recompense, a master to coerce that duty, and convert him into a useful and valuable servant.
“I maintain that it is not injustice to leave the negro in the condition in which nature placed him; in this there is no injustice. The master can compel him to labor, and thereby afford to that master a just compensation in return for the care and talent employed in governing him. In this way alone is the negro enabled to render himself useful to himself and to the society in which he is placed.”
Stephens promoted the idea of the perpetuation and expansion of the institution of slavery as a positive good.
Lincoln was elected on a platform of preventing its expansion with the eventual goal of its abolition due to its being a great evil.
If there was no difference between these two positions, why did the southern states feel compelled to secede to protect their peculiar institution when Lincoln was elected?
I’m still waiting for anybody to post contemporaneous southern disagreement with the Cornerstone Speech, which I contend received no such disagreement because it perfectly expressed the conventional wisdom in the South.
If the South was indeed moving towards eventual abolition, such disagreement shouldn’t be hard to find.
Good luck.