I have studied this issue thoroughly from Islamic sources and I think that there are huge mental leaps in your answer to the Captain. The point is that Quran and Hadiths have categorically allowed sex with as many slave girls as desired by a Muslim or in his possesion. This allowance is unconditional with no reference to any restriction based on the condition of the economy of the Muslim state. Neither they direct any where that the practice should be gradually given up.
Under the reign of Hadhrath Ummar, the second Khalifa, the economy of the Islamic state was so sound that no one could be found to pay zakah to (in fact this sound economy was also based on huge income from slave trade and khumus to Baithul Mal from spoils of war, which also included men and women captured in war). Still concubanage and sex with slave girls was practiced.
Moreover, if drinking wine could be abruptly disbanded, why not slavery? At least a certain condition could've been laid down for practicing slavery. And why sex with women captured in war was allowed? Was it not enough that the captured girls did physical labor in her master's house? Why was she also forced to provide sexual pleasures to the master in addition to the physical labor extracted out of her (because she had been captured in war)? In some cases husbands of the women captured were alive but the women was separated from the husband and given in slavery to a soldier, who also had the right to sell her any where he wanted. Could not the approach to this problem be more human, allowing both the captured woman and her husband to live together, to continue serving the master, and not to subject her to the indiginity of forced sex and agony of separation from husband and disintegration of family?
Hope you will provide me a satisfactory answer and help me retain my Iman." />