I think arguing about societal norms differing over a thousand years misses the point, really. The Quran, and Muhammad's actions as he lived by it, are supposed to be the pinnacle of morality, the guidelines that everyone looks back on as they try to live their own lives. The argument that societal values have changed over time ignores the supposition that morality is absolute, that what Allah says is good must be good. Since Allah decreed (as Ibrahim pointed out) that Aisha was to be married to Muhammad, it is divine will that that happen. Either that is morally wrong, or it is morally right - and since it is Allah's will that it happen, it is clearly morally right. This, in my mind, is a far more troublesome issue. A lot of things can be forgiven when you simply say the people involved lived in different times (I've seen it said for things like the US founders having slaves, for instance), but divine morality is absolute and unchanging, so the values of then must be the values of now, which obviously renders a lot of things 'good' that are by modern standards unpalatable.