The jihadis are not acting in an “extremist” manner in this. The seizure of Infidel girls and their use as sex slaves is sanctioned in the Qur’an. According to Islamic law, Muslim men can take “captives of the right hand” (Qur’an 4:3, 4:24, 33:50). The Qur’an says: “O Prophet! Lo! We have made lawful for you your wives to whom you have paid their dowries, and those whom your right hand possesses of those whom Allah has given you as spoils of war” (33:50). 4:3 and 4:24 extend this privilege to Muslim men in general. The Qur’an says that a man may have sex with his wives and with these slave girls: “The believers must win through, those who humble themselves in their prayers; who avoid vain talk; who are active in deeds of charity; who abstain from sex, except with those joined to them in the marriage bond, or the captives whom their right hands possess, for in their case they are free from blame.” (Qur’an 23:1-6)
The rape of captive women is also sanctioned in Islamic tradition:
Abu Sirma said to Abu Sa’id al Khadri (Allah he pleased with him): 0 Abu Sa’id, did you hear Allah’s Messenger (may peace be upon him) mentioning al-’azl? He said: Yes, and added: We went out with Allah’s Messenger (may peace be upon him) on the expedition to the Bi’l-Mustaliq and took captive some excellent Arab women; and we desired them, for we were suffering from the absence of our wives, (but at the same time) we also desired ransom for them. So we decided to have sexual intercourse with them but by observing ‘azl (Withdrawing the male sexual organ before emission of semen to avoid conception). But we said: We are doing an act whereas Allah’s Messenger is amongst us; why not ask him? So we asked Allah’s Messenger (may peace be upon him), and he said: It does not matter if you do not do it, for every soul that is to be born up to the Day of Resurrection will be born. (Sahih Muslim 3371)
It is also in Islamic law: “When a child or a woman is taken captive, they become slaves by the fact of capture, and the woman’s previous marriage is immediately annulled.” (Umdat al-Salik O9.13)
The Egyptian Sheikh Abu-Ishaq al-Huwayni declared in May 2011 that “we are in the era of jihad,” and that meant Muslims would take slaves. In a subsequent interview he elaborated:
Jihad is only between Muslims and infidels. Spoils, slaves, and prisoners are only to be taken in war between Muslims and infidels. Muslims in the past conquered, invaded, and took over countries. This is agreed to by all scholars—there is no disagreement on this from any of them, from the smallest to the largest, on the issue of taking spoils and prisoners. The prisoners and spoils are distributed among the fighters, which includes men, women, children, wealth, and so on.