A Race Through Dark Places provides the show's one and only hint at the history of the Psi Corps:
Sheridan to Garibaldi: Well, you've been pretty quiet. Is [Bester] right, or isn't he?
Garibaldi: Technically? Yeah, I suppose. We're obliged to uphold the laws of Earth Alliance. It doesn't mean we have to like it. And if there is some kind of illegitimate travel going through here, it's a threat to station security and we have to know about it.
Ivanova: Come on, Garibaldi. You can't tell me you agree with this. You want to help them?
Garibaldi: Want, agree, that has nothing to do with it. The law is the law. It's damn ironic, isn't it? The Corps got started because we were afraid of telepaths, now they're victims of our own fears. We took away every right they had and shoved them into a big black box called Psi Corps. Now look at them. Black uniforms, jackboots, giving orders. Some days they scare the hell out of me.
Sheridan: Yeah, if you ask me we created our own monster. And maybe we deserve it.
But this curiously missing history is actually very well-known in-universe, even if the show isn't telling you much about it:
2272. The Hague. (Gregory Keyes, Final Reckoning, p. 241-242)
Prosecutor (EA Senator Semparat): "Who declared this war? You?"
Bester raised an eyebrow mildly. "The terrorists declared it when they bombed our facilities on Mars. Everything we did after that was response, kind for kind."
"We've heard evidence that you, Alfred Bester, murdered civilians long before the beginning of the telepath conflict. Are you going to claim that that was war, as well?"
"Of course," Bester said.
"I, for one, am confused by that statement, Mr. Bester, and my guess is that many of this court are equally confused. Would you care to explain?"
"I would be delighted to, Senator," Bester replied.
"Please do so then."
Bester took a sip of the water next to him. "One hundred and fifty-eight years ago, the existence of telepaths was known to almost no one. One hundred and fifty-seven years ago, it became common knowledge thanks to an article in the New England Journal of Medicine.
"By the end of that year, eighteen thousand telepaths were dead. No war was declared by any government. They were killed one at a time, they were killed en masse and buried in pits, they were aborted when DNA testing revealed what they were as fetuses."
"Mr. Bester, I'm sure we all know the history."
Maybe we need to know a little more about it, if we're going to understand what we're seeing in the show?
Are those telepaths actually fleeing the Corps, as implied - or the Earth Alliance?
Didn't Garibaldi just admit that it's Earth Alliance law that prevents telepaths from leaving?
Continuing from the trial, above:
"This undeclared, unrecognized war has been fought for a hundred and fifty-seven years. Its casualties - have always been on my side. And when this killing began, what did EarthGov do about it? They built a telepath ghetto called Teeptown, and they gave us badges to mark us, separate us. They gave any normal who wanted to kill a telepath the means to find us and identify us. Then they used telepaths to control telepaths. Why? The implicit threat was always there - ask any telepath old enough to remember. Either you control yourselves, or we will control you.
"That was the choice I grew up with. Hunt down and sometimes kill my own kind, with the blessings of EarthGov and every normal citizen who voted for it, or be subjected to the same uncontrolled genocide that was visited on us in the beginning."
Sounds like there's a story here.
Let's talk a bit about genocide, shall we? Especially since Garibaldi's trying to make veiled comparisons between the Corps and the Nazis, when the reverse is true.
Dr. Gregory H. Stanton, a professor at Mary Washington University and the Vice President of the International Association of Genocide Scholars, and the head of Genocide Watch, a non-profit organization dedicated to the fight against genocide, wrote "Eight Stages of Genocide" in 2006, later revised to the Ten Stages of Genocide in 2013. We're going to talk about the first four stages, because for about 150 years, not much changed in EA law vis-à-vis telepaths. In the early 22nd century, the leadership of the Earth Alliance very quickly (and simultaneously) moved through the first four stages, but then hit "pause" on the condition of a "devil's bargain" with the telepath population: Either you 'control' yourselves, or we will 'control' you. Either you do our bidding, even kill your own kind for us, or we will wipe you all out.
Prior to this period, normals and telepaths lived side by side, without incident. Telepaths had equal rights - legally, socially, politically. No one "registered" them, no one banned them from employment or from holding political office, no one forced them to dress differently, and no one forced them to attend separate schools. Normals did indeed, as Garibaldi reluctantly admits, "take away every right they had," including the right to leave. And with no offense intended to Mr. Bester (or Gregory Keyes), the circumstances that led to this dramatic social change are just a bit more complicated than one article published in one medical journal.
The first four stages of genocide, according to Professor Stanton, are as follows:
Classification: All cultures have categories to distinguish people into “us and them” by ethnicity, race, religion, or nationality.
Prior to "classification," those later called "telepaths" lived as members of their respective communities. Even as some developed abilities stronger than had ever existed in the past, nothing significant occurred for generations. People peacefully coexisted.
Symbolization: We give names or other symbols to the classifications. We name people “Jews” or “Gypsies”, or distinguish them by colors or dress; and apply the symbols to members of groups. Classification and symbolization are universally human and do not necessarily result in genocide unless they lead to dehumanization. When combined with hatred, symbols may be forced upon unwilling members of pariah groups: the yellow star for Jews under Nazi rule, the blue scarf for people from the Eastern Zone in Khmer Rouge Cambodia.
With the Crawford-Tokash Act and other "telepath registration" laws of the early 22nd century, telepaths were required to register with the government, and to dress differently from the normal population in order to set them apart: to wear black leather gloves when out in public, and to wear the "psi insignia" on their clothes.
Discrimination: A dominant group uses law, custom, and political power to deny the rights of other groups. The powerless group may not be accorded full civil rights or even citizenship. Examples include the Nuremberg Laws of 1935 in Nazi Germany, which stripped Jews of their German citizenship, and prohibited their employment by the government and by universities.
Under the same laws, telepaths were barred from certain areas of employment and social participation (e.g. sport), until eventually they were barred from all employment outside the Corps (unless they took "sleeper" drugs). Telepaths who refused to take the drugs or join the Corps were imprisoned indefinitely.
Telepaths were stripped of the right to hold public office or sit on juries. They were stripped of the right to a criminal trial or to an attorney, and of the right against self-incrimination. Other laws classified telepaths as not fully "human," but as simultaneously both humans and non-human "devices," subject to regulation like other technology.
Though initially telepaths were still permitted to serve in the armed forces (in a limited capacity), this right, too, was eventually abolished. Telepath children and teenagers were forced to attend separate (boarding) schools. "Teeptown" in Geneva was constructed as a ghetto. When first contact with the Centauri occurred, giving Earth access to jumpgate technology, telepaths were banned from leaving Earth Alliance space.
Telepaths were regularly enslaved, abused, trafficked and even murdered by criminal syndicates, and the normal police turned a blind eye.
Many laws (in both the civil and criminal contexts) were passed that gave normals new rights to be "free from" unwanted contact with telepaths (e.g. in criminal investigations or trials), or with so-called "rogue" telepaths (at work, in public places, etc.). Both tort law and the rules of evidence underwent substantial transformation to address the new "telepath threat." The free speech of telepaths was substantially curtailed.
Dehumanization: One group denies the humanity of the other group. Members of it are equated with animals, vermin, insects or diseases. Dehumanization overcomes the normal human revulsion against murder. At this stage, hate propaganda in print and on hate radios is used to vilify the victim group.
Propaganda against telepaths was broad in scope. Telepathy was compared to, among other things, rape, trespass, theft and cheating. Parents were encouraged to abort if their fetuses carried the genetic marker for telepathy (though most who carry it, it was later learned, do not grow up telepathic). Propaganda contributed to the wide-spread belief that telepaths wear gloves because to touch them would be physically dangerous, making them literally "untouchables." Telepaths were also presented as plotting a vast international conspiracy to take over the Earth economy, courts and the government, even though they comprised at most a tenth of a percent of the population and were subjected to extreme discrimination. Panic among the normal population led to draconian laws forcing telepaths out of "normal" society and subjecting them to harsh punishments for minor "transgressions," such as refusing to wear the psi insignia or gloves. A vicious cycle formed wherein the laws became self-justifying, and Earth Alliance policy that classified telepaths legally as "devices" rather than as people allowed courts to suspend what constitutional rights telepaths used to have, and to support new anti-telepath measures.
Earth created a caste system: people, and telepaths.