I think it depends on the context. If you turn the tables on your own abuser, then I'd almost call it justified, to an extent. However, if you abuse an innocent, then it's absolutely not justified. Then you have something like rape and sexual abuse and that's inexcusable, no matter what trauma a person has been through and I consider there to be no leeway.

I can agree with that. I definitely don't give any leeway with rape & sexual abuse; like the person in question should know what rape & sexual abuse does to people. How could he/she inflict that on someone else. I see turning the tables on an abuser as more of a self-defense thing. I can understand how an abused person can abuse an innocent but as you said, it's not justifiable.