I'm an American and have been living and teaching in China for about a year.

I have never been accosted by a police officer in China. The authorities here are actually less intrusive than police in America. You will notice this as soon as you reach arrivals at a Chinese airport; security is very lax. I brought a desktop computer from the US through airport security in Shanghai and nobody stopped me to even bother checking it.

I once locked myself out of my apartment and the building security couldn't get me in so they called the police. The police officer that showed up called a locksmith for me. Once the locksmith had managed to get the door open, the police officer asked to see my passport. The officer took a quick look at my visa and left without even asking to enter my apartment.

Every time I have been inside a Chinese police station, half the people in the office are wearing shorts and t-shirts, smoking, and shooting the breeze while only a handful seem to be doing any actual work. The police in China simply can't be troubled unless a serious crime has been committed, or a foreigner or connected Chinese person need something done.

Understand that nothing is done by the book around here. Ordinary people in China break the law constantly in all sorts of ways (although violent crime is quite rare.) The authorities are responsive to public political provocation, but they let all sorts of little things slide that people could never get away with in America (e.g., parking your car on the sidewalk - technically illegal, and yet you can't walk on a lot of the sidewalks because they are full of cars.)

Unless you really go out of your way to rock the boat the authorities here are happy to leave you alone.