By Denis G. Rancourt
For the same reason that it is so difficult for a slave to recognize that he/she is a slave! 
A first step is for the (wage, economic, or other) slave to recognize -- beyond the master's grip on the mental and emotional environment -- that he/she is a slave. Even this consciousness can only be substantively attained through the process (praxis) itself of liberation; this too the master knows.
There may result a spontaneous impulse to escape from physical oppression but liberation is much more than escape. Mere escape from physical and economic oppression is not the full ontological freedom that is fulfillment and purpose; and that is contagious and exhilarating.
Since consciousness and liberation are always possible and can lead to a social chain reaction if radical nuclei are not quickly identified, isolated, and destroyed, and since such nucleation is frequent and widespread in slaves left to think for themselves, the hierarchy of dominance that we inhabit must create and maintain an illusion of the danger of freedom.
The establishment's mantra in this regard -- which resonates incessantly in the halls of all law schools and between the walls of all philosophy and ethics classrooms -- is the hollow statement that "freedom is always at the expense of the freedoms of others".
In the language of the Canadian Charter of Rights and Freedoms this becomes:
"The Canadian Charter of Rights and Freedoms guarantees the rights and freedoms set out in it subject only to such reasonable limits prescribed by law as can be demonstrably justified in a free and democratic society."
And the courts are the arbitrator of this fantasy. For example, in a recent Supreme Court of Canada ruling about libel law we have:
"The exercise as a whole involves balancing freedom of expression, freedom of the press, the protection of reputation, privacy concerns, and the public interest. Each of these is a complex value protected either directly or indirectly by the Canadian Charter of Rights and Freedoms. Weighing these often competing constitutional interests is a legal determination. It is, therefore, a determination that the judge should undertake [not a jury!?]."
-- (2009, Grant vs TorStarCorp)
Judges are always "balancing". Note how in this ruling a jury cannot decide the weight attributed to "the public interest", that "privacy concerns" usually relate to an employer's "labour relations", to corporate management and to solicitor-client privilege, that those who can afford to sue for libel and slander have money, and that the mainstream press is owned by the same economic masters that determine the rest, including the economic apartheid of the working class and surplus peoples.
"The law, in its majestic equality, forbids rich and poor alike to sleep under bridges, to beg in the streets, and to steal their bread."
-- Anatole France
The system's mantra "freedom is always at the expense of the freedoms of others" is hollow because it purposely abstracts away the omnipresent relation of dominance; the asymmetry of power between the individual drawn to freedom and the oppressive system bent on maintaining dominance.
The mantra is often accompanied with the nightmarish fairy tale that humans left to satiate their primal impulses would ravage unprotected humanity. The word "chaos" often comes up. The immediate conclusion of course is that one needs the master's protection; that the slaves themselves are to be feared by other slaves. That more police and prisons are needed, etc.
Everyone has the experience of dominance and its effects on otherwise healthy persons and so everyone can relate to the "need" to be protected...
Let's see. If I use my freedom of expression how does this occur at the expense of the freedoms of others? Does the fact of my expression prevent others from expressing themselves? If I am too loud and persistent won't my audience walk away? If I am speaking loudly in a library is my expression preventing others from speaking loudly in the library? I may be asked to leave and I may be expelled by force but have I impinged on the freedoms of expression of others? It is not my expression that has caused me to be expelled. It is my bad choice of venue and my aggression against community members collectively seeking tranquility.
Similarly, if as the professor in a classroom I choose to express racist views does this act prevent other professors from expressing whatever views they wish? No. Does it oppress the targeted minority students in the classroom? Yes. The oppression comes from the asymmetry of power and influence, not from the expressed views themselves. Black students may express the same views among themselves in an authentic and exploratory discourse without there being any racism of oppression. 
My freedom of expression does not mask my oppression-of-dominance of individuals or groups. The expression component remains expression and the oppression is oppression. Let us not confuse the expression with the oppression. Let us hone our ability to recognize and name hierarchical oppression and not become language police. Let us not displace our capacity to sense manipulation and coercion in favor of language and expression purification.
"Words that wound" are an artifice of new-wave law theorists looking to lead a legal analysis sect premised on slave-hood and the law as protective master and paternalistic guardian of society's values. Here Henry Louis Gates Jr.'s deconstruction of critical race theory is a breath of fresh air but does not go far enough regarding hierarchy. 
No one and no group has an ontological right to oppress. It's not about balancing freedoms. It's about getting freedom.
"Nobody can give you freedom. Nobody can give you equality or justice or anything. If you're a man, you take it."
-- Malcolm X
"Taking it" is "positive freedom", not just the "negative" freedom from oppression, but actuation of freedom.
Isaiah Berlin put it this way :
"The ‘positive’ sense of the word ‘liberty’ derives from the wish on the part of the individual to be his own master. I wish my life and decisions to depend on myself, not on external forces of whatever kind. I wish to be the instrument of my own, not of other men’s acts of will. I wish to be a subject, not an object; to be moved by reasons, by conscious purposes which are my own, not by causes which affect me, as it were, from outside. I wish to be somebody, not nobody; a doer – deciding, not being decided for, self-directed and not acted upon by external nature or by other men as if I were a thing, or an animal, or a slave incapable of playing a human role, that is, of conceiving goals and policies of my own and realizing them. This is at least part of what I mean when I say that I am rational, and that it is my reason that distinguishes me as a human being from the rest of the world. I wish, above all, to be conscious of myself as a thinking, willing, active being, bearing responsibility for his choices and able to explain them by reference to his own ideas and purposes. I feel free to the degree that I believe this to be true, and enslaved to the degree that I am made to realize that it is not."
This is in line with Paulo Freire's liberation :
"Freedom is acquired by conquest, not by gift. It must be pursued constantly and responsibly. Freedom is not an ideal located outside of man; nor is it an idea which becomes myth. It is rather the indispensable condition for the quest for human completion. [...] If people, as historical beings necessarily engaged with other people in a movement of inquiry, did not control that movement, it would be (and is) a violation of their humanity. Any situation in which some individuals prevent others from engaging in the process of inquiry is one of violence. The means used are not important; to alienate human beings from their own decision-making is to change them into objects."
Regarding the legal system's sanitized freedom rights balancing act diversion that conveniently disappears the relation of oppression, Derrick Jensen has this to say :
"It comes down to a basic truism: defensive rights always trump offensive rights. My right to freedom always trumps your right to exploit me, and if you do try to exploit me, I have the right to stop you, even at the expense of you."
Now think who exploits who in our little dominance hierarchy over here where we live... Who is in jail for what? Who kills the most people? Who gets away with selling death to all? Who has a license to print money? Who sues who and who wins at it? Who has a voice? Who decides?
 "Pedagogy of the Oppressed" by Paolo Freire, 1970.
 "How anti-racism protects class structure and dominance hierarchy" by Denis G. Rancourt, 2011.
 "Critical Race Theory and Freedom of Speech" by Henry Louis Gates Jr., 1996. In: "The Future of Academic Freedom", edited by Louis Menard.
 "Two Concepts of Liberty" by Isaiah Berlin, 1958.
 Preface by Derrick Jensen to the 2007 edition of "Pacifism as Pathology" by Ward Churchill.
Denis G. Rancourt is a former tenured and full professor of physics at the University of Ottawa in Canada. He practiced several areas of science (including physics and environmental science) which were funded by a national agency and ran an internationally recognized laboratory. He has published over 100 articles in leading scientific journals and several social commentary essays. He developed popular activism courses and was an outspoken critic of the university administration and a defender of student and Palestinian rights. He was fired for his dissidence in 2009. His dismissal case is in court hearings that will extend into 2012.