How does forced unpaid labour and rape rehabilitate someone?! What a load of bollocks. And the rest of that is bollocks to. The verse he is referring to is talking about prostitution (as in actual prostitution where the slave is made to have sex with other men and her owner takes the money made) -
Yusufali: "Let those who find not the wherewithal for marriage keep themselves chaste, until God gives them means out of His grace. And if any of your slaves ask for a deed in writing (to enable them to earn their freedom for a certain sum), give them such a deed if ye know any good in them: yea, give them something yourselves out of the means which God has given to you. But force not your maids to prostitution when they desire chastity, in order that ye may make a gain in the goods of this life. But if anyone compels them, yet, after such compulsion, is God, Oft-Forgiving, Most Merciful (to them), (The Noble Quran, 24:33)"
Not to mention the Quran makes it legal to have sex with slave girls in other verses, so it cannot be referred to as prostitution in this sense. Ibn Kathir provides a clarification of verse 24:33-
[(And force not your slave-girls to prostitution...) Among the people of the Jahiliyyah, there were some who, if he had a slave-girl, he would send her out to commit Zina and would charge money for that, which he would take from her every time. When Islam came, Allah forbade the believers to do that?..]
This link explains it quite well-
http://www.islam-watch.org/MA_Khan/FarzanRapingSlave.htm