Regardless of consent, sex and pregnancy at age 9-12 is something only a fool would advocate.
I think it quite likely that a millennia ago, wise elders of the tribe would have known things of this sort.
Muslims citing, "that's how things were back then", is not only tacit approval of their prophet being a child rapist, it also puts them into the awkward position of knowing that it is *not* appropriate and it is not 'right' for an adult to rape a child and that it both risks children's lives physically as well as causes them numerous neuropsychiatric disorders in adulthood, having to consider the fact that if their prophet was genuinely talking to their god and their god was genuinely communicating regularly with their prophet, wouldn't god have known the harm that child rape does and have advised him not to rape Aisha?
So citing "that's how things were" is to say that either their prophet wasn't actually communicating with god and he was simply making sure he got what he wanted by lying to his deluded followers, or god also approved of child rape back then but doesn't now.
Either that or they have to claim that their god did and still does approve of child rape.
We're sort of saying the same thing, but I'm trying to give some allowance for different cultural and different times.
As an aside, the phrase "Child Bride" exists as a term, because historically there were enough cases of it to cause it to be termed distinctly.
We can apply today's knowledge to man's actions of long ago, and thus be critical of those actions.
Would a "God" a millennia ago have advised a person he was communicating with not to "rape Aisha?"
It is not possible for me to answer a question of this sort, since as an atheist I find the premises in error, and therefore the conclusions would be without value.
For what it's worth, here is the Wikipedia entry on Aisha.
https://en.wikipedia.org/wiki/Aisha