I don't understand the episode where peralta harasses and unlawfully arrests the guy in the patrolman union thing (might be different because where I live the police are respected, not trying to insult American police)

He ran after being asked to be questioned, in a suspicious setting where it very well could have resulted in a bomber escaping, and after good evidence peralta wasn't trying to intimidate him. Sorry if this view is wrong. Pls educate me