Generally citizens doing things against other citizens doesn't seem to be dealt with all that harshly (as opposed to citizens doing things against the state, or - worse - encouraging other citizens to do so).
I've seen domestic violence dealt with in China by putting the victim and perpetrator in a jail cell together and telling them to talk it out.
The harshest sentences are reserved for those who refuse to participate in official corruption. Citizens-on-citizens is sort of intramural.
This latter attitude is familiar in the US. When mostly black people were killing mostly other black people over drug turf wars, it was not treated very seriously. You may imagine that in China, anybody who is not a party member doesn't deserve much attention.
