I don't think a human action being particularly atrocious or surprising equates to mental retardation. You could argue that killing thousands in the atrocious and awful methods they do makes them less "human" or not "normal" but mental handicapped refers to an intellectual disability en.wikipedia.org/wiki/Intellectual_disability. There have been MANY very very smart (read: not intellectual challenged) people who have done awful things and have been deluded into believing awful things. So no I do not.
Women's conduct is mostly surprising. Just read this so called love story of a Malaysian 26 old female doc who left to Syria to join ISIS and "war on western world" buzzfeed.com/ellievhall/an-isis-love-story-till-martyr...part#.wdwqgN5gg5. I saw no ideological motives in her story. Instead I saw some strange woman, trying just to find a husband among ISIS fighters who stick to this "wisdom": "the goal of an ISIS couple is to be together in Jannah (the Islamic heaven) not in this life". All in all, this isn't the worst scenario for a woman in ISIS. I know some stories when wives of the killed ISIS fighters were sold into some brothels in Africa or used as suicide bombers. In most cases those are European women that enjoy "the honor".