Is that link speaking with authority, or was it speculation that these virgin girls were kept as slaves to help Israelite women? What happened to these virgin girls when they got older? Were they let go? Were they sold to others?
What of the young boys? Would they not have been able to serve a function as well, even in the role of slavery?
And when Moses is telling the MEN to kill the young boys and unclean women, isn't he still speaking to the men when he said for them to "keep the virgins for yourself"? There is nothing in there about then being told to bring them to your house as slaves to help the women folk.
I understand what the link is saying about the "sexual immorality", but I'm sure it would BE immoral to have relations with a woman who wasn't a virgin, who would have been the ones that these men were committing adultery with. For them to take virgins, they would be pure and clean in that respect. For us today, we may see it as immorality. But I wonder if THEY, . . .back then, saw the taking of virgins (to add to their household) as immoral. Remember, even wives weren't much more than property at that time either.