Sexual slavery is nothing unique in war zones. Problem in this instance is that many condemn the practice but condone the principle of “right hand possessions”. Result will be today its ISIS, tomorrow there will be someone else, who’ll be maligning Islam/muslims with that principle. Only solution is to condemn practice and principle, otherwise you’ll always be prone to someone else utilizing the principle later on.
Reforms are needed, all the time, but too many reject the notion of reforms, because then they would not be following a “perfect” religion perhaps? Religions should be about spiritual enlightenment and personal growth, not warfare rules and regulations anyway.