How to reply to the suspicions concerning woman slavery(captives)?
 
1_ In the bible 
In reply to the suspicions concerning women slavery (female captives) 

Deuteronomy 20:10-18 New International Version (NIV) 
 
10 When you march up to attack a city, make its people an offer of peace. 11 If they accept and open their gates, all the people in it shall be subject to forced labor and shall work for you. 12 If they refuse to make peace and they engage you in battle, lay siege to that city. 13 When the Lord your God delivers it into your hand, put to the sword all the men in it. 14 As for the women, the children, the livestock and everything else in the city, you may take these as plunder for yourselves. And you may use the plunder the Lord your God gives you from your enemies. 15 This is how you are to treat all the cities that are at a distance from you and do not belong to the nations nearby. 
 
Based on the heavenly law set by God in the Bible, " As for the women, the children, the livestock and everything else in the city, you may take these as plunder for yourselves. And you may use the plunder the Lord your God gives you from your enemies." 
This law is set by God, so how can you Christian brother/sister object to it? 
The Ten Commandments order us to respect slaves (captives) .

 
Exodus 20:17 King James Version (KJV) 
17 Thou shalt not covet thy neighbour's house, thou shalt not covet thy neighbour's wife, nor his manservant, nor his maidservant, nor his ox, nor his ass, nor any thing that is thy neighbour's. 

 
Although the Christian law orders us to worship the ONE God and not to carve an idol for us, many people violate these commandments. What confirms the continuity of the legislation of  female slaves (captives) in the Bible , is the order of the Lord himself, "Don’t desire  your relative's woman, not only this, but also don’t desire your relatives maidservent (captives).!! 
 

Deuteronomy 21:10-14 New International Version (NIV) .
Marrying a Captive Woman 
 
10 When you go to war against your enemies and the Lord your God delivers them into your hands and you take captives, 11 if you notice among the captives a beautiful woman and are attracted to her, you may take her as your wife. 12 Bring her into your home and have her shave her head, trim her nails 13 and put aside the clothes she was wearing when captured. After she has lived in your house and mourned her father and mother for a full month, then you may go to her and be her husband and she shall be your wife. 14 If you are not pleased with her, let her go wherever she wishes. You must not sell her or treat her as a slave, since you have dishonored her .
 
The Lord has inspired this to Moses: a complete law about captivity and captive women!! The interpretations confirm the  existence of captive women and not only that, but a man must shave her head, trim her nails and take off her clothes so that her appearance becomes very bad and then marry her without the permission of her parents and she has no rights.

2_In Islam 

Imam Bukhari (2547)

Narrated Abu Musa Al-Ash`ari: The Prophet said, "He who has a slave-girl and teaches her good manners and improves her education and then manumits and marries her, will get a double reward; and any slave who observes Allah's right and his master's right will get a double reward."

You see; that’s how Islam set the course of emancipating slaves. They should definitely be well treated. Also, educating female captives and marrying them, after emancipation is considered an act of charity, which would earn one great reward. Not only that. Islam further puts an end to the habit of using derogative names of “slaves” or “servants”. In Islam, man must not show servitude to anyone besides Allah the Almighty. So it was stipulated that the captives should be addressed by “fatah” (boy) or “fatat” (girl). Besides, the act of emancipating slaves used to be a competitive work among the Prophet’s Companions, for it was highly recommended by Islam and was considered an act of worship.

Abu Huraira reported Allah's Messenger (?) as saying:

None of you should say: My bondman and my slave-girl, for all of you are the bondmen of Allah, and all your women are the slave-girls of Allah; but say: My servant, my girl, and my young man and my young girl.

Reference : Sahih Muslim 2249 a

Islam treated female slaves more kindly in their enslavement than other cultures did. Their honour was not considered to be permissible to anyone by a way of prostitution, which was the fate of female prisoners of war in most cases. Rather Islam made them the property of their masters alone, and forbidden anyone else to also have an intercourse with them.