I think it's important to note that Bobby Fischer was paranoid and delusional. While he was definitely arrested and injured, his exact claims here should be viewed sceptically.
Person is stopped on the street because of looking like suspect. On closer look, doesn't actually look like suspect but acts oddly and invites police to arrest him. They arrest him, and are not gentle with the handcuffs or putting him into the car. The actual suspect is caught elsewhere, but Bobby is arrested on suspicion of acting oddly, not of being the bank robber, so no reason to let him go. The part about choking him during interrogation, I dunno, anyway they interrogated him and were unsatisfied. Placed naked into empty cell with the light on seems like normal procedure (whether that's right or wrong) for someone arrested for behaving oddly; then being transferred to solitary doesn't seem out of the norm either. That they were considering sending him to a mental hospital and concerned about suicide is consistent with that treatment. Bobby offers that he was doing a lot of screaming and what not during this time. Eventually, someone in charge takes a look in and asks direct questions and Bobby gets his clothes back and his phone call and released.
This isn't treatment I'd like to have, and I'd like for it not to be normal, but unfortunately, it's pretty much normal, so I don't think there's a whole lot to be skeptical about --- with the exception of the choking. That could have happened, or it might not have, I don't know if that was really normal or not; I think a lot of interrogations are now video recorded for many reasons, but probably not in 1981
Edit: I want to be clear here, the police can absolutely be abusive to paranoid people, and people struggling with mental illness might seem to be acting suspiciously or weirdly by the police who have no training in dealing with mental health. It's very possible Bobby was acting oddly though non criminaly and the police totally mishandled it, he certainly shouldn't have been arrested. But his exact claims of what happened need to be viewed with the knowledge he frequently made false accusations throughout his life.
This in itself is a conscious choice. Someone had chosen not to train the officers.