“Any kind of discrimination — be it on grounds of religion, political opinion, race, or whatever it is — seems to be incompatible with the idea of freedom under the law. Experience has shown that separate never is equal and cannot be equal.”

Remarks by President Obama and President Kenyatta of Kenya in a Press Conference at Kenyan State House in Nairobi, Kenya https://www.whitehouse.gov/the-press-office/2015/07/25/remarks-president-obama-and-president-kenyatta-kenya-press-conference (July 25, 2015)
2015
Context: I believe in the principle of treating people equally under the law, and that they are deserving of equal protection under the law and that the state should not discriminate against people based on their sexual orientation. And I say that, recognizing that there may be people who have different religious or cultural beliefs. But the issue is how does the state operate relative to people. If you look at the history of countries around the world, when you start treating people differently -- not because of any harm they’re doing anybody, but because they’re different -- that’s the path whereby freedoms begin to erode and bad things happen. And when a government gets in the habit of treating people differently, those habits can spread. And as an African-American in the United States, I am painfully aware of the history of what happens when people are treated differently, under the law, and there were all sorts of rationalizations that were provided by the power structure for decades in the United States for segregation and Jim Crow and slavery, and they were wrong.

Pt. III, Ch. 19 : The Right to Ignore the State, § 1 http://oll.libertyfund.org/titles/273#lf0331_label_200
Social Statics (1851)
Context: As a corollary to the proposition that all institutions must be subordinated to the law of equal freedom, we cannot choose but admit the right of the citizen to adopt a condition of voluntary outlawry. If every man has freedom to do all that he wills, provided he infringes not the equal freedom of any other man, then he is free to drop connection with the state — to relinquish its protection, and to refuse paying towards its support. It is self-evident that in so behaving he in no way trenches upon the liberty of others; for his position is a passive one; and whilst passive he cannot become an aggressor. It is equally selfevident that he cannot be compelled to continue one of a political corporation, without a breach of the moral law, seeing that citizenship involves payment of taxes; and the taking away of a man’s property against his will, is an infringement of his rights. Government being simply an agent employed in common by a number of individuals to secure to them certain advantages, the very nature of the connection implies that it is for each to say whether he will employ such an agent or not. If any one of them determines to ignore this mutual-safety confederation, nothing can be said except that he loses all claim to its good offices, and exposes himself to the danger of maltreatment — a thing he is quite at liberty to do if he likes. He cannot be coerced into political combination without a breach of the law of equal freedom; he can withdraw from it without committing any such breach; and he has therefore a right so to withdraw.

2010s, America: One Nation, Indivisible (2015)

#23
1900s, Maxims for Revolutionists (1903)

Source: Speech (June 1853), p. 79

Remarks by President Obama and Daw Aung San Suu Kyi of Burma in Joint Press Conference at Aung San Suu Kyi Residence in Rangoon, Burma on November 14, 2014 http://www.whitehouse.gov/the-press-office/2014/11/14/remarks-president-obama-and-daw-aung-san-suu-kyi-burma-joint-press-confe
2014

2000s, The Logic of the Colorblind Constitution (2004)
Context: Harlan's dissenting opinion in Plessy, that the Constitution was colorblind, and that it did not countenance different and unequal classes of citizens, was based upon a belief in the truth of the principle of equality in which the founders and Lincoln had so profoundly believed. But this belief had been buried by progressivism, and has not been resurrected, except by the intellectual heirs of Leo Strauss. On intellectual grounds, it has never been refuted, and ought never to have been abandoned. There is not now, and never has been any such difference between one human being and another human being, or whatever race or color, such that one is by nature the ruler of the other, as any human being is by nature the ruler of any dog or any horse. For this reason, legitimate political authority can arise only by the consent of the governed, and consent can never be given for any reason other than the equal protection of the rights of the governed. Hence equal protection is the foundation of all constitutionalism, even apart from its specific inclusion in the Constitution itself. For more reasons than one, Justice Harlan's dissenting opinion ought to have been the opinion of the Court in 1896; even more ought it to have been the opinion of the Court in 1954. As Professor Edward J. Erler has demonstrated in the pages of the Claremont Review of Books, the principle of equal protection has never become the opinion of the Supreme Court of the United States, nor has it been favored in the writings of conservative jurists.

The Civil Rights Act of 1997 http://www.fed-soc.org/publications/detail/the-civil-rights-act-of-1997 (December 1, 1997)

“Milton Friedman vs Free Lunch Advocate” https://www.youtube.com/watch?v=9Qe7fLL25AQ (1980s)