It should be clear that whilst we are all responsible to help, only the abuser is actually to blame.
I disagree. Anybody who has the ability to do something to rectify a situation and doesn’t shares responsibility for the outcome. Of course, the perpetrator himself takes the lion share of the blame, and would have to be either a sick, perverted individual or an ill person. People who can do something about it and don’t are not as bad in the sense that they are not doing deliberate damage; their inaction generally comes from more innocent origins: misguided judgment, cowardice, laziness, a heap of cognitive bias, and often the “bystander effect” (individuals will only take necessary action in a place where it is obvious to them that they are the only ones who can; in a situation where there are others who could do the same, nobody does it). But although you can split up the motives of the people responsible (evil v. misguided), everybody takes blame.