Muhammad Sallalahu Allaihi Wassalam married Aisha RA and the age of six and she started living with him at the age of 9 once she became mature.
The marriage was a revelation from allah. Aisha RA had wisdom beyond her age and was ready to live with the Nabi of Allah Sallalahu Allaihi Wassalam. That is sufficient for us muslims to know. Many people become defensive over this and try to make things palatable for the Kuffaar world, no need for this, leave that to the Christian priests. We love and cherish our Nabi like nothing else in this world and nothing they say will change that.
They speak about 6 and 9 yrs, if I knew I would get a daughter and the Nabi of Allah asked her hand in marriage, then forget about 9 and 6 yrs, I would confirm the marriage when my daughter is still in her mothers womb. I know for a fact that the Nabi of Allah Sallalahu Allaihi Wassalam will take better care of her than I as a father will ever be able to do. Her life both in this world and the next would be made.
They are speaking against that Nabi, which gave his entire life for this ummah, even at the time of death he asked the Malaikah of death to give him the pangs of death of his entire ummah so that none of them would suffer. Even on the day of Qiyamah, when people won't find anyone to help, all other Ambiya, will resolve themselves from this task, Muhammad Sallalahu Allaihi Wassalam, will be saying, Ya ummati, Ya ummati.
One of the companion's of prophet Muhammad (sallallahu alayhi wa sallam) asked: "On the day of Judgement, where shall we find you?" Muhammad (sallallahu alayhi wa sallam) replied: "I will meet you at three places on the day of Judgement: The Scale, the River Kawthar, and the Bridge."
I have heard narrations were the Nabi of Allah, will tip the scales in ones favour using his hand, at the river Kawthar he will be giving his ummah water with his own hands, at the bridge (Pulsiraat) he will be pulling people out of the fire by grabbing them around their waist. We are prepared to sacrifice every drop of our blood for the sake of our Nabi. They should'nt think they can brainwash us and reduce the honour of our Nabi in our eyes. Impossible.