Why don't they (the majority of muslims) say hadith about her being 9 yrs old are false? Surely that would help to project him as the perfect man and role model. Why not do the same to other controversial subjects regarding him too? Both of those would be better than 'covering up' what she went through, no?
You've just answered your own question, and explained how hagiography works, and hinted on what prevents this happening, and the tensions and moral contortions that faces the believer in Islam today like never before.
For example, to simply deny any of it happened at all opens up a complete abyss for Islam, because with emptiness and nothingness as far as the life and narrative of Muhammad is concerned, what is Islam predicated on at all?
Let me explain further.
The accepted narratives of Islamic canon regarding Muhammad are what we're talking about - the situation on its own terms.Lets use Aisha to illustrate this.
The accepted canon states certain things - the age of both Muhammad and Aisha at the consummation of the marriage.
A defence of Mo as stated by devilsadvokat suggests that nowhere in the accepted canon of Islamic narrative does it state that Aisha was unhappy or objected as a minor to being married and having intercourse with a 50 year old man.
One doesn't follow the other.
Lets refer to Saffiya again.
Accepted Islamic canon says her husband and family and community were all killed at Mohammad's behest, and soon afterwards, she was having sex with the man who killed her loved ones, and married her as 'war booty'
That is Islam's claim. All Muslims believe this action to be 'fact'.
By using our imagination about what it would be like to see your husband, and community killed, and then be taken as 'war booty', married to the perpetrator of the killing, and be having sex with him very soon afterwards (I think just one or two days later), we can at the very minimum, imagine that it might not have been a nice thing, and that Saffiya didn't have personal choice and autonomy, and that any expression as such is unlikely to feature in the hagiography that becomes Islamic narrative on the life of Muhammad.
Remember, we're discussing the assertions made specifically on actions of Muhammad, by the standard carrative canon that all Muslims believe in. There is another discussion to be had about whether it happened at all thats for another time.
Will write more later on this if you like.