Fight what? No one wants to know. Pretty much all of us are fed up of fighting. We have to fight for everything, especially once they hear a diagnosis of autism you are on your own. There is nothing to fight because there is nothing there.
This.
You have an appointment where you get given a diagnosis and a leaflet. The one given to us was simply titled "autism" and was 3-4 pages explaining what autism is, how autism is diagnosed, and that was it. Utterly useless. After your appointment and your meeting they send you on your way, discharged. If you want further help or support you need to seek it out yourself via books, the internet, and charities/support groups if there are any in your locality. Lord help you if your child needs any follow up care or ongoing support, funding has been cut to the bone and then cut some more so what little support does exist is often at the end of a very long waiting list and not always fit for purpose.
One of my DC has a restricted diet with only around 10-12 foods that he will eat including chicken dippers, cornflakes, apples, and plain pasta.
It is not down to fussy eating, poor parenting, lack of choices, or stubbornness.
He WILL literally starve himself if no acceptable foods are available.
As well as acceptable foods, they must be prepared and presented in a specific way. For example, the chicken dippers must be Birds Eye and he knows if they're not (Birds Eye are softest/least fibrous), the cornflakes must be in whole milk and must be left to go totally soggy before eating, the pasta must be fusilli only, apples the red ones only and the softer kind not crisp/crunchy. He has to have specific bowls/plates/cups, specific cutlery, the food must be arranged on his plate with none of it touching.
If any of it is wrong by his standards then you can't just correct the offending item, the whole meal is ruined and he won't eat any of it. It is exhausting keeping on top of it all, making sure he has a multivitamin each day - we're lucky and he will have a vitamin right now but as he gets older who knows if he will still comply? - trying to calm him down if it isn't right. We have tried to introduce new foods following the advice of the dietician by putting them on his plate alongside safe foods, this resulted in every meal containing a new food to be entirely rejected as its presence on the plate ruined the rest (and they're not even "new" foods, they're the foods the rest of the family eat so not entirely alien to him). We tried putting the new foods in a separate dish alongside his safe plate and he would end up in hysterics refusing to come to the table. For the time being he is only eating safe foods as he needed a break from the stress of it.
Anyone on this thread saying that this boy's parents could have done more, that they are to blame, that they should have force fed him, and so on haven't gotten the first clue what it is they are talking about and it shows.