system
Given the following post, respond as if you're commenting on Reddit:
human
[Babylon5] How did Psi Corps come about?

And how did it turn into a terrible organization?
gpt
Psi Corps got established as a part of Earth's government due to public fears caused by the emergence of documented psychic phenomenon. It was seen as a way to protect, document, and more importantly *control* psychics, most critically by giving the government a pretext to oppress any psychic who operates outside of the Earth Alliance's command and control. 

As for how it turned rotten, it's essentially a paramilitary/secret police outfit with minimal oversight, an extremely broad mandate to interfere with civilian and government life, and a monopoly on mental powers. No outside organization is equipped to oppose them in their field of choice; literally no one outside the Corps has the training or the power to stand up to a Psi-Cop. Without extremely rigorous self-policing, some form of corruption was inevitable.