Provided you differentiate feeling sorry for the victims and wanting the perpetrators brought to justice, I don't think there's any real social obligation to feel sorry for victims. Wanting justice can be justified by considering the corrosive effect crimes have on society as a whole, even though the direct victims don't deserve sympathy. For instance, when gangsters massacre other gangsters, I don't feel sorry for the victims (who lived by the sword, then died by it) but this lack of empathy for the victims doesn't temper my desire to see the perpetrators brought to justice.
The trap is when you don't care about the perpetrators facing justice because you think the victims deserved it. That's a bad path to go down.
Provided you differentiate feeling sorry for the victims and wanting the perpetrators brought to justice, I don't think there's any real social obligation to feel sorry for victims. Wanting justice can be justified by considering the corrosive effect crimes have on society as a whole, even though the direct victims don't deserve sympathy. For instance, when gangsters massacre other gangsters, I don't feel sorry for the victims (who lived by the sword, then died by it) but this lack of empathy for the victims doesn't temper my desire to see the perpetrators brought to justice.
The trap is when you don't care about the perpetrators facing justice because you think the victims deserved it. That's a bad path to go down.