It's seen as bad to punch people. If someone is punching you and punching them back will get them to stop, generally most people would think it's ok to punch them back. That doesn't mean punching is good. It means that sometimes doing a bad thing (punching people) may be need and does not always make you bad as an individual.
Unless you are a complete pacifist and against self defense of any kind (including restricting freedom of movement such as imprisonment), I'm not really sure why you'd disagree.
Doing bad things to bad people does not make you good, but it doesn't make you inherently bad.