First of all, there is absolutely no mention of “forced brides”, “sex slaves”, or selling on any “black market”. Believe it or not, those are all things you’ll find in the Qur’an, but not in this story (feel free to scrutinize Number 31). So, it’s especially ironic that you is trying to ascribe to the Bible exactly that which is actually found in the Qur’an (see the following verses in the Qur’an: 33:50, 23:5-6, 4:24, 24:32) and in the Hadith (see Bukhari 62:137, where female captives are taken as slaves and raped with Mohammed’s approval; or Bukhari 34:432, where
Mohammed is asked about coitus interruptus because they’re worried about devaluing their female captives if they get pregnant and have to be sold for less money; or Abu Dawud 2150, which quotes Qur’an 4:24 to allow people to rape women in front of their husbands as part of capture). Talk about psychological projection…

Second, as for the killing of women and leaving the virgins alive, it has nothing to do with sex, slavery, or anything like that. It has to do with
self-preservation. In those times, when two nations warred, it was to the death. There was no “UN” to send “peacekeepers” to monitor ceasefires. If two nations
had it out for one another, they wouldn’t stop until the other nation was entirely killed. Why? Because if you left some of them alive, they would eventually come back at you (kind of like modern-day Israel’s mistake with Hamas the last few times they battled them—the stupid, morally bankrupt, short-sighted UN seemed to think that in forcing Israel to leave Hamas intact, that Hamas would somehow really give up terrorism and play nice, when in reality they will never stop killing Jews until they are completely wiped out!). So, that’s why the Bible describes how all males were killed of all ages, and women were only spared if they were virgins, i.e., they weren’t sleeping with and getting pregnant by the enemy, and having offspring that would later come back for revenge. It’s a simple as that, and nothing spectacularly unusual when it comes to warring nations in those days.

Third, What is written there in full context is that God has them separate out a percentage of ALL the booty to give to the LEVITES, which being God’s priests, are
interchangeably referred to by God as “for me” and “for the Levites”. And, furthermore, the cattle, sheep, possessions, and yes, women, were not given to the Levites as sex slaves. They were given under their charge—and that could be for any number of purposes: to work in the Tabernacle, to assimilate into the tribe, etc.

In fact, the proof of this interpretation is found by an exact parallel in Exodus, Chapter 13, and in Deuteronomy, Chapter 15. In both those places, God commands Israel to separate out every firstborn “for Him”, whether man or animal. Obviously, this doesn’t mean God or the Levite priests plans to have sex with every first-born guy or animal,
as this you would have you believe. It means that every first-born is meant to work in the Tabernacle, under the direction of the Levite priests. (And, although we don’t have a Tabernacle or Temple anymore, still even to this day, all Jews still have the first-born redemption ceremony involving the Levites, for every non-Levite first-born! Side note: one example of someone dedicated at birth to the Levites was Samuel, as described in I Samuel, Chapter 1. As you can clearly see, it was to serve in the Temple, not to get “raped” by God, or whatever you are claiming.)

So, again, this whole sexualising Number 31 is a manipulative, underhanded attempt by a you to pull the wool over the eyes of people who might not know the Bible that well, so as to deflect from the REAL sick stuff that’s actually IN THE QUR’AN!