Alfieisnoisy
I think you understood what I meant by moderation vs moderators deleting posts. It amounts to the same thing.
Posters jumping straight to the 'your child Must have behaviour which caused the situation in school' but these opinions wouldn't have been deleted for a typical child QED the OP is being 'shielded' because of her son's difficulties and that isn't fair. If you post on AIBU, you're asking for differing view points. If you want lots of people telling you that you're right and the world is wrong then find some millennials for a yoga session.
"when occasionally my son retaliated"
Retaliation is retaliation. Every child is held to different standards but physical retaliation needs to be an uncrossed line. Last week, I used the phrase "you idiot, now you'll be punished too" when a child crossed that retaliation threshold. It sums it up.
"This didn't stop some posters automatically diving in and blaming her child."
No. It didn't stop people questioning what happened and looking to suggest alternatives to an OP talking about their angel child who does no wrong etc. Again, exactly the same way any other OP would be.
You want to stop the parent of any child with disabilities being questioned. That isn't the way it works in real life and the internet sure as hell isn't a safe space for back-rubbing, hand-holding and filtered opinions.
The bullying you talk about needs considered separately to your child's problems. The grandparent's behaviour (in the OP) needs to be considered outside of the OP's circumstances. If a GC is being treated badly by the OP's son that that's what they care about. No child is perfect. The OP thinks their child is and that's improbable and deleting posts which question this point of view shouldn't be deleted. Obviously you think they should and nothing which goes against your ideas should be allowed to be written, but you're wrong.
Vickibee
I sympathise. I really do. Trust me though, your child does wrong as does any other and going through life thinking they're perfect and never in the wrong will do neither of you any favours.
"Leaving a thread" because you don't like some comments won't expose you to ideas and thoughts beyond your own. It may be hard to read or think about, but you'll have a wider idea of the situation by reading and thinking about it all.
In my experience, children get more tolerant of "irritating and annoying" children with age. People are accepted for their idiosyncrasies. Sometimes celebrated for them.