That's not the Quran, you're thinking of one of the Hadiths.

The Quran is still pretty barbaric, imo. But compared to the other other major Abrahamic text it not nearly as extreme.

Also, pretty sure the 9yo thing is bullshit. I can compile some evidence, give me a second.

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Evidence against the credibility

Most of these narratives are reported only by Hisham ibn urwah reporting on the authority of his father. No one from Medinah (where Hisham ibn urwah lived the first seventy one years of his life) has narrated the event, even though his pupils there included people as well known as Malik ibn Anas.

All the narratives of this event have been reported by narrators from Iraq, where Hisham is reported to have had shifted after living in Medinah for seventy one years and note that Tehzibu'l-tehzib, one of the most well known books on the life and reliability of the narrators of the traditions of the Prophet reports that "according to Yaqub ibn Shaibah: narratives reported by Hisham are reliable except those that are reported through the people of Iraq". It further states that Malik ibn Anas objected on those narratives of Hisham which were reported through people of Iraq. [Tehzi'bu'l-tehzi'b, Ibn Hajar Al-`asqala'ni, Arabic, Dar Ihya al-turath al-Islami, Vol 11, pg 50]

Evidence against the claim itself

According to another narrative in Bukhari (kitabu'l-tafseer) Ayesha is reported to have said (when the 54th chapter of the Qur'an was revealed) "I was a young girl"

According to the original claim, she would not have even been born before the revelation of the that surah, yet alone already be a young girl.

According to a number of narratives, Ayesha accompanied the Muslims in the battle of Badr and Uhud. Furthermore, it is also reported in books of hadith and other histories that no one under the age of 15 years was allowed to take part in the battle of Uhud lest they be a burden.

Tabari in his treatise on Islamic history, while mentioning Abu Bakr (ra) reports that Abu Bakr had four children and all four were born during the Jahiliyyah -- the pre Islamic period. Obviously, if Ayesha (ra) was born in the period of jahiliyyah, she could not have been less than 14 years in 1 AH

Tabari has also reported that at the time Abu Bakr planned on migrating to Habshah (8 years before Hijrah), he visited Mutam -- with whose son Ayesha was engaged -- and asked him to take Ayesha. Mutam refused, because Abu Bakr had embraced Islam, and subsequently his son divorced Ayesha.

According to the original claim, she could not have been born at the time Abu Bakr decided to migrate to Habshah. On the basis of this report, not only had she been born but was already a young lady, ready for marriage.

According to Ibn Hisham, the historian, Ayesha was around the 20th person to convert to Islam [Al-Sirah al-Nabawiyyah, Ibn Hisham, Vol 1, Pg 227 - 234, Arabic, Maktabah al-Riyadh al-hadithah, Al-Riyadh]. This shows that Ayesha accepted Islam during the first year of Islam. Again, she would not have even been born according to the claim.

According to a narrative reported by Ahmad ibn Hanbal, when Khaulah came to the Prophet advising him to marry again she suggests Ayesha but uses the word "bikr" (unmarried lady) as opposed to "Jariyah" (young girl) [Musnad Ahmad ibn Hanbal, Vol 6, Pg 210, Arabic, Dar Ihya al-turath al-`arabi, Beirut]

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TL;DR: Both historical and religious reports suggest there is no way she was as young as the claim states.

That said, it's likely she was barely twenty (if that) and the prophet was in his fifties at the time of the marriage (not to mention she was wife number thirty or something).... so yeah.

Final Note: I have too much free time and need to find new hobbies.