In the story, Leonard Mead is out walking. He encounters no one on his walk, but this is not unusual for his city. This is because all the inhabitants of his city appear to be glued to their televisions. Leonard Mead exists in a classic, dystopian world, where everyone must conform to the status quo. No one seems to sell newspapers, books, or magazines any more. Similar to the totalitarian world in Fahrenheit 451, reading is unheard of.
When Leonard responds that he is a writer, the robotic police car notes that he has no profession. Since no one reads, there can be no such thing as writers. This is a dehumanizing assessment of Leonard, but he shrugs it off. When questioned as to why he is out alone, Leonard responds that he has enjoyed a daily evening walk for years. Sadly, this is enough to incriminate Leonard.
So, the police car takes Leonard to the Psychiatric Center for Research on Regressive Tendencies because he has not conformed to the expectations of the law. It is apparent that everyone is expected to be enthralled by the television programs that have been especially tailored for public consumption. Failure to comply is accounted as rebellion and a sort of societal heresy. In this sense, Leonard has 'regressed' or reverted to the old ways, when individuality was still tolerated. In a totalitarian society, any deviation from the norm is unerringly punished, and this is what happens here. The police car does not tolerate any argument from Leonard in defense for his actions; it merely whisks the bewildered man away.