http://quran.com/18/60-82From what I can understand, the Al-Khidr guy killed a young boy for apparently no reason and Moses was shocked and called him abhorrent for doing so. But then later Moses finds out that al-Khidr knew that the kid was an atheist (god had created him that way in advance) and was probably gonna corrupt his family and the entire town, so god ordered Al-Kihidr to kill the poor lad and it was actually a really good thing for everyone as described in the apologetics below.
I really couldn't believe the shit written in the commentary attempting to excuse this..
http://www.al-islam.org/faith-and-reason-ayatullah-mahdi-hadavi-tehrani/question-43-al-khidr%E2%80%99s-actions-qur%E2%80%99Basically:
1. Its good for the prophet cos he gets to kill someone for god
2. Its good for the boy's parents cos they don't get led to hell by their son.
3. And its good for the young boy, cos he is prevented from being an evil atheist in the future and he gets to burn in hell forever.
So if al Khidr does it Moses (rightly) thinks its abhorrent, but when god does it its the best thing since sliced foreskins.