Samael_Khan
Goosebender
Do you only care for those who have personal meaning to you? You would be okay if a group of people you don't know, were kidnapped and sold into slavery in the sex trade market and you heard about that? I think most people would care. Empathy is a human quality that evolution gave us. We identify ourselves with the plight of others, even those we don't personally know, out of basic human responses.
This is a great video I think you should watch. It's all science based, even though he makes the remark about religion getting certain things right upon occasion. It might help to change your perspective a bit on this. I'm sure you're not that detached from your empathy for others to say you just don't care.
Science shows that empathy is a tribal thing. That is why tribalism exists. At the moment we are trying to overcome that as a global society. The further away from the tribe someone is the less empathy you have for them.
As for me, in principle I am against sex slavery, and if I hear someone get dragged into it I have a feeling of disgust and righteous indignation. But that is momentary. The evidence that I don't care that much about it is that I don't take action to sort out the situation or at least feel the urge to.