This sort of religious permission for rape is nothing new, it’s an ancient tradition. In wartime many women will voluntarily offer sex as a morale booster for men on their side. In the United States, during World War II, there were thousands of "V-Girls" or "Victory Girls," who might be more accurately described as "war groupies." These young women were willing to give their all for the boys in uniform. This practice was not condoned by any (or at least not many) American clergy at the time.
Every war has its V-Girls and that includes the war on terror. Despite the severe restrictions on women in the Islamic world, there have long been reports of Moslem V-Girls. The official permission for such behavior is complicated by the fact that just about any Moslem can issue a fatwas. The more senior Islamic scholars and clerics are constantly trying to neutralize the effects of self-proclaimed "religious authorities" issuing defective (in terms of law or interpretation) fatwas. This has become a serious problem with the availability of satellite television and radio, which can spread a bad fatwa (like one that falsely accuses someone of being a heretic and calls on all Moslems to try and kill the poor guy). This was never a problem in pre-radio days. Back then, a fatwa was simply a religious interpretation (or just opinion) given to a small group of people or an individual. But now, an inspiring (and often unscrupulous) preacher can get on satellite TV or a radio show and issue all manner of religiously incorrect and dangerous fatwas.
The government of Saudi Arabia is trying to counter this by getting large numbers of Sunni religious scholars to agree on some standards for who can issue a fatwa, and what a fatwa can do. This is no small matter to Islamic scholars, and the Saudis are spending a lot of money to transport (to Saudi Arabia) and house (in fine style) the most respected Islamic scholars for conferences on the fatwa issue. Shia Islam has less of a problem with this because their clergy is more highly organized with a widely recognized hierarchy of clerics.
Despite that, Islam has never had a central power that could decide organizational or religious issues. There are many sects, and some are murderously hostile to each other. Westerners like to say that what Islam needs is a Martin Luther (the Christian cleric who got the Protestant Reformation going 500 years ago). But in this case, what Islam really needs is a pope, someone who has the final word on all these religious arguments. When Islamic radicals get to arguing over these matters, their final argument is often murder, not another theological interpretation.