An Argumentum ad Victis is a form of the argumentum ad misericordium, an appeal to emotion in combination with the argumentum ad hominem. In the Argumentum ad Victis, the validity or appropriateness of arguing against, or criticizing the claim of, one who presents herself as a victim is ruled out of bounds.
The Argumentum ad Victis, rather than being an appeal to emotion is a tactic of intimidation. The victim is held as being unquestionable and without fault. You cannot criticize a victim, because they are a victim. You cannot test the truth of their claims, because they are . . . a victim. Any perceived criticism is held to be a savage attack upon the victim himself and justification for their future actions, including libel and slander.
Here is how it works in practice:
Victim shares her experience suffering physical and emotional abuse at the hands of her husband.
Respondent wonders about the depth of abuse and asks questions seeking corroboration.
(Victim's) Friend responds in high dudgeon, saying that you shouldn't criticize Victim or say she's lying because she has been really, really hurt. Really hurt.
Respondent replies that she didn't say Victim was lying, only asked for corroborating evidence.
Victim/Friend reply that this sort of inexcusably horrible and unChristian treatment is exactly why she has rejected "X" or done "Y".