To cower a population, it is not necessary to arrest and convict everyone, what you have to do is to perform in an arbitrary and capricious manner and people will generally censor themselves. Naomi Wolf has written in The End of America about how she has been arbitrarily detained, no doubt because of her political actions and statements. She has a slew of recent stories in the U.S., with a nod to other chilling parallels, such as Nazi Germany where governments arbitrarily detain and release citizens.
Now comes this story about a guy, an ordinary Joe, who was arbitrarily detained and released, after his sign was confiscated and then returned. This is an ominous occurrence.