“Humanity ends when there is a disregard for the rights of others and a denial of the existence of others”
Related quotes

“Human entirety can only be what it is when giving up the addiction to others’ ends.”
Source: On Nietzsche (1945), p. xxxiv, note

Individuality http://www.infidels.org/library/historical/robert_ingersoll/individuality.html (1873).
Context: The Declaration of Independence announces the sublime truth, that all power comes from the people. This was a denial, and the first denial of a nation, of the infamous dogma that God confers the right upon one man to govern others. It was the first grand assertion of the dignity of the human race. It declared the governed to be the source of power, and in fact denied the authority of any and all gods. Through the ages of slavery — through the weary centuries of the lash and chain, God was the acknowledged ruler of the world. To enthrone man, was to dethrone God.

"Our Universal Civilization" in The New York Times (5 November 1990) https://www.nytimes.com/1990/11/05/opinion/our-universal-civilization.html
Context: The universal civilization has been a long time in the making. It wasn't always universal; it wasn't always as attractive as it is today. The expansion of Europe gave it for at least three centuries a racial taint, which still causes pain. … This idea of the pursuit of happiness is at the heart of the attractiveness of the civilization to so many outside it or on its periphery. I find it marvelous to contemplate to what an extent, after two centuries, and after the terrible history of the earlier part of this century, the idea has come to a kind of fruition. It is an elastic idea; it fits all men. It implies a certain kind of society, a certain kind of awakened spirit. I don't imagine my father's Hindu parents would have been able to understand the idea. So much is contained in it: the idea of the individual, responsibility, choice, the life of the intellect, the idea of vocation and perfectibility and achievement. It is an immense human idea. It cannot be reduced to a fixed system. It cannot generate fanaticism. But it is known to exist, and because of that, other more rigid systems in the end blow away.

“For the nonbeliever, on the other hand, to deprive a man of his life is to end his existence.”
God’s Justice and Ours http://www.firstthings.com/article/2007/01/gods-justice-and-ours-32, 123 First Things 17. (May 2002).
2000s
Context: It seems to me that the more Christian a country is the less likely it is to regard the death penalty as immoral. Abolition has taken its firmest hold in post-Christian Europe, and has least support in the church-going United States. I attribute that to the fact that, for the believing Christian, death is no big deal. Intentionally killing an innocent person is a big deal: it is a grave sin, which causes one to lose his soul. But losing this life, in exchange for the next? The Christian attitude is reflected in the words Robert Bolt’s play has Thomas More saying to the headsman: 'Friend, be not afraid of your office. You send me to God'. For the nonbeliever, on the other hand, to deprive a man of his life is to end his existence.

1960s, Special message to Congress on the right to vote (1965)
Context: In our system, the first right and most vital of all our fights is the right to vote. Jefferson described the elective franchise as "the ark of our safety." It is from the exercise of this right that the guarantee of all our other rights flows. Unless the right to vote be secure and undenied, all other rights are insecure and subject to denial for all our citizens. The challenge to this right is a challenge to America itself. We must meet this challenge as decisively as we would meet a challenge mounted against our land from enemies abroad.