“In ordinary circumstances, contradictions among the people are not antagonistic. However, if they are not handled properly, or if we relax our vigilance and lower our guard, antagonism may arise. In a socialist country, a development of this kind is usually only a localized and temporary phenomenon. The reason is that the system of exploitation of man by man has been abolished and the interests of the people are the same.”

Progress, Coexistence and Intellectual Freedom (1968), Dangers, Pollution of Environment
Context: The problem of geohygiene (earth hygiene) is highly complex and closely tied to economic and social problems. This problem can therefore not be solved on a national and especially not on a local basis. The salvation of our en­vironment requires that we overcome our divisions and the pressure of temporary, local interests. Otherwise, the Soviet Union will poison the United States with its wastes and vice versa.

Speech at the 5th Congress of the Polish United Workers Party (12 November 1968), quoted in The Rise and Fall of the Brezhnev Doctrine in Soviet Foreign Policy (2003) by Matthew J. Ouimet

On Contradiction (1937)
Original: (zh-CN) 共产党内正确思想和错误思想的矛盾，如前所说，在阶级存在的时候，这是阶级矛盾对于党内的反映。这种矛盾，在开始的时候，或在个别的问题上，并不一定马上表现为对抗性的。但随着阶级斗争的发展，这种矛盾也就可能发展为对抗性的。苏联共产党的历史告诉我们：列宁、斯大林的正确思想和托洛茨基、布哈林等人的错误思想的矛盾，在开始的时候还没有表现为对抗的形式，但随后就发展为对抗的了。中国共产党的历史也有过这样的情形。我们党内许多同志的正确思想和陈独秀、张国焘等人的错误思想的矛盾，在开始的时候也没有表现为对抗的形式，但随后就发展为对抗的了。目前我们党内的正确思想和错误思想的矛盾，没有表现为对抗的形式，如果犯错误的同志能够改正自己的错误，那就不会发展为对抗性的东西。因此，党一方面必须对于错误思想进行严肃的斗争，另方面又必须充分地给犯错误的同志留有自己觉悟的机会。在这样的情况下，过火的斗争，显然是不适当的。但如果犯错误的人坚持错误，并扩大下去，这种矛盾也就存在着发展为对抗性的东西的可能性

Hansard, House of Commons, 6th Series, vol. 45, col. 316.
Maiden speech as MP for Sedgefield, 6 July 1983.
1980s

Source: Bellum Catilinae (c. 44 BC), Chapter XXXIII, section 5

Collected Works, Vol. 24, pp. 398–421.
Collected Works

Speech made at the Reichstag (21 May 1935) Found in Translation of Herr Hitler's Speech to the German Reichstag on May 21, 1935 https://books.google.com/books?id=r_-htwAACAAJ&dq=hitler+may+21+1935+speech&hl=en&sa=X&ved=0ahUKEwir0MTAmInWAhXPaCYKHaFIB2UQ6AEIJjAA Foreign Office Press. German version https://archive.org/stream/RedeDesFhrersUndReichskanzlersAdolfHitlerVorDemReichstagAm21.Mai/MicrosoftWord-Ah19350521#page/n11/mode/2up
1930s
Context: The Germany of today is a National Socialist State. The ideology that dominates us is in diametrical contradiction to that of Soviet Russia. National Socialism is a doctrine that has reference exclusively to the German people. Bolshevism lays stress on international mission. We National Socialists believe a man can, in the long run, be happy only among his own people. We are convinced the happiness and achievements of Europe are indissolubly tied up with the continuation of the system of independent and free national States. Bolshevism preaches the establishment of a world empire and recognizes only section of a central international. We National Socialists grant each people the right to its own inner life according to its needs and its own nature. Bolshevism, on the other hand, establishes doctrinal theories that are to be accepted by all peoples, regardless of their particular essence, their special nature, traditions, etc. National Socialism speaks up for the solution of social problems, issues and tensions in their own nation, with methods that are consistent with our common human, spiritual, cultural and economic beliefs, traditions and conditions. Bolshevism preaches the international class struggle, the international world revolution with the weapons of the terror and the violence. National Socialism fights for the reconciliation and consequent adjustment of the differences in life and the union of all for common benefits. Bolshevism teaches the overcoming of an alleged class rule by the dictatorship of the power of a different class. National Socialism does not attach importance to a only theoretical rule of the working class, but especially on the practical improvement of their living conditions and standard of living. Bolshevism fights for a theory and, for it, sacrifices millions of people, immense values of traditional culture and traditions, and achieves, compared with us, only a very low standard of living for all. As National Socialists, our hearts are full with admiration and respect for the great achievements of the past, not only in our own people but also far beyond. We are happy to belong to an European cultural community that has so tremendously embossed today's world with a stamp of its mind. Bolshevism rejects this cultural achievement of mankind, claiming that has found the beginning of the real cultural and human history in the year of birth of Marxism. We, National Socialists, do not want to be of the same opinion as our church organizations in this or that organizational question. But we never want a lack of belief in religion or any faith, and do not wish that our churches become club-houses or cinemas. Bolshevism teaches the godlessness and acts accordingly. We National Socialists see in private property a higher level of human economic development that according to the differences in performance controls the management of what has been accomplished enabling and guaranteeing the advantage of a higher standard of living for everyone. Bolshevism destroys not only private property but also private initiative and the readiness to shoulder responsibility. It has not been able to save millions of human beings from starvation in Russia, the greatest Agrarian State in the world. It would be unthinkable to transfer such a catastrophe into Germany, because, at the of the day, in Russia there are 10 city dwellers for every 90 country dwellers, but in Germany for only 25 farmers there are 75 city dwellers. National Socialists and Bolshevists both are convinced they are a world apart from each other and their differences can never be bridged. Apart from that, there were thousands of our people slain and maimed in the fight against Bolshevism. If Russia likes Bolshevism it is not our affair, but if Bolshevism casts its nets over to Germany, then we will fight it tooth and nail.

The Elements of Moral Philosophy (McGraw-Hill, 1999), p. 95

Concurring opinion, Yates v. United States, 354 U.S. 298 (1957).