The Washington Post published his manifesto 20 years ago. Here is part of it:
When we speak of leftists in this article we have in mind mainly socialists, collectivists, “politically correct” types, feminists, gay and disability activists, animal rights activists and the like. But not everyone who is associated with one of these movements is a leftist. What we are trying to get at in discussing leftism is not so much movement or an ideology as a psychological type, or rather a collection of related types…. The two psychological tendencies that underlie modern leftism we call “feelings of inferiority” and “oversocialization.”….
11. When someone interprets as derogatory almost anything that is said about him (or about groups with whom he identifies) we conclude that he has inferiority feelings or low self-esteem. This tendency is pronounced among minority rights activists, whether or not they belong to the minority groups whose rights they defend. They are hypersensitive about the words used to designate minorities and about anything that is said concerning minorities. The terms “negro,” “oriental,” “handicapped” or “chick” for an African, an Asian, a disabled person or a woman originally had no derogatory connotation. “Broad” and “chick” were merely the feminine equivalents of “guy,” “dude” or “fellow.” The negative connotations have been attached to these terms by the activists themselves. Some animal rights activists have gone so far as to reject the word “pet” and insist on its replacement by “animal companion.” Leftish anthropologists go to great lengths to avoid saying anything about primitive peoples that could conceivably be interpreted as negative. They want to replace the world “primitive” by “nonliterate.” They seem almost paranoid about anything that might suggest that any primitive culture is inferior to our own. (We do not mean to imply that primitive cultures ARE inferior to ours. We merely point out the hypersensitivity of leftish anthropologists.)
12. Those who are most sensitive about “politically incorrect” terminology are not the average black ghetto- dweller, Asian immigrant, abused woman or disabled person, but a minority of activists, many of whom do not even belong to any “oppressed” group but come from privileged strata of society. Political correctness has its stronghold among university professors, who have secure employment with comfortable salaries, and the majority of whom are heterosexual white males from middle- to upper-middle-class families.
13. Many leftists have an intense identification with the problems of groups that have an image of being weak (women), defeated (American Indians), repellent (homosexuals) or otherwise inferior. The leftists themselves feel that these groups are inferior. They would never admit to themselves that they have such feelings, but it is precisely because they do see these groups as inferior that they identify with their problems. (We do not mean to suggest that women, Indians, etc. ARE inferior; we are only making a point about leftist psychology.)
14. Feminists are desperately anxious to prove that women are as strong and as capable as men. Clearly they are nagged by a fear that women may NOT be as strong and as capable as men.
15. Leftists tend to hate anything that has an image of being strong, good and successful. They hate America, they hate Western civilization, they hate white males, they hate rationality. The reasons that leftists give for hating the West, etc. clearly do not correspond with their real motives. They SAY they hate the West because it is warlike, imperialistic, sexist, ethnocentric and so forth, but where these same faults appear in socialist countries or in primitive cultures, the leftist finds excuses for them, or at best he GRUDGINGLY admits that they exist; whereas he ENTHUSIASTICALLY points out (and often greatly exaggerates) these faults where they appear in Western civilization. Thus it is clear that these faults are not the leftist’s real motive for hating America and the West. He hates America and the West because they are strong and successful.
16. Words like “self-confidence,” “self-reliance,” “initiative,” “enterprise,” “optimism,” etc., play little role in the liberal and leftist vocabulary. The leftist is anti-individualistic, pro-collectivist. He wants society to solve everyone’s problems for them, satisfy everyone’s needs for them, take care of them. He is not the sort of person who has an inner sense of confidence in his ability to solve his own problems and satisfy his own needs. The leftist is antagonistic to the concept of competition because, deep inside, he feels like a loser.
17. Art forms that appeal to modern leftish intellectuals tend to focus on sordidness, defeat and despair, or else they take an orgiastic tone, throwing off rational control as if there were no hope of accomplishing anything through rational calculation and all that was left was to immerse oneself in the sensations of the moment.
18. Modern leftish philosophers tend to dismiss reason, science, objective reality and to insist that everything is culturally relative. It is true that one can ask serious questions about the foundations of scientific knowledge and about how, if at all, the concept of objective reality can be defined. But it is obvious that modern leftish philosophers are not simply cool-headed logicians systematically analyzing the foundations of knowledge. They are deeply involved emotionally in their attack on truth and reality. They attack these concepts because of their own psychological needs. For one thing, their attack is an outlet for hostility, and, to the extent that it is successful, it satisfies the drive for power. More importantly, the leftist hates science and rationality because they classify certain beliefs as true (i.e., successful, superior) and other beliefs as false (i.e., failed, inferior). The leftist’s feelings of inferiority run so deep that he cannot tolerate any classification of some things as successful or superior and other things as failed or inferior. This also underlies the rejection by many leftists of the concept of mental illness and of the utility of IQ tests. Leftists are antagonistic to genetic explanations of human abilities or behavior because such explanations tend to make some persons appear superior or inferior to others. Leftists prefer to give society the credit or blame for an individual’s ability or lack of it. Thus if a person is “inferior” it is not his fault, but society’s, because he has not been brought up properly.
19. The leftist is not typically the kind of person whose feelings of inferiority make him a braggart, an egotist, a bully, a self-promoter, a ruthless competitor. This kind of person has not wholly lost faith in himself. He has a deficit in his sense of power and self-worth, but he can still conceive of himself as having the capacity to be strong, and his efforts to make himself strong produce his unpleasant behavior.  But the leftist is too far gone for that. His feelings of inferiority are so ingrained that he cannot conceive of himself as individually strong and valuable. Hence the collectivism of the leftist. He can feel strong only as a member of a large organization or a mass movement with which he identifies himself.
20. Notice the masochistic tendency of leftist tactics. Leftists protest by lying down in front of vehicles, they intentionally provoke police or racists to abuse them, etc. These tactics may often be effective, but many leftists use them not as a means to an end but because they PREFER masochistic tactics. Self-hatred is a leftist trait.
21. Leftists may claim that their activism is motivated by compassion or by moral principles, and moral principle does play a role for the leftist of the oversocialized type. But compassion and moral principle cannot be the main motives for leftist activism. Hostility is too prominent a component of leftist behavior; so is the drive for power. Moreover, much leftist behavior is not rationally calculated to be of benefit to the people whom the leftists claim to be trying to help. For example, if one believes that affirmative action is good for black people, does it make sense to demand affirmative action in hostile or dogmatic terms? Obviously it would be more productive to take a diplomatic and conciliatory approach that would make at least verbal and symbolic concessions to white people who think that affirmative action discriminates against them. But leftist activists do not take such an approach because it would not satisfy their emotional needs. Helping black people is not their real goal. Instead, race problems serve as an excuse for them to express their own hostility and frustrated need for power. In doing so they actually harm black people, because the activists’ hostile attitude toward the white majority tends to intensify race hatred.
22. If our society had no social problems at all, the leftists would have to INVENT problems in order to provide themselves with an excuse for making a fuss.