The autistic boy in the story, Hikaru, entered school after a year of integrated preschool. He found it really hard to adjust to school. Although he adjusted after awhile, for months he was crying much of the time. People would comment on it all the time.
Another example is the following, gotten from here:
"Anna stopped smiling and laughing for the entire four years she was on Vigabatrin, but started smiling again within a week after we discontinued it. We eliminated it because of our concerns about possible vision loss"
Hikaru's mother, Sachiko, was portrayed as a very caring and understanding mother of her autistic son. I don't know much about Anna's father, but I assume he cares deeply about his daughter as well. But there seems to be a much greater tolerance for suffering of developmentally disabled children than other children. My mother even shows this. When I cry or self-injure, she doesn't get as concerned as someone who doesn't know me would get. (By the way, in case I haven't stressed this enough, these are good parents. My mother and Sachiko and presumably Anna's father are all good parents. That's part of the problem - even good people act this way.)
I'm not sure why there is this tolerance for suffering. Considering the kind of people who act this way, it's obviously not hate or uncaring. And it's unlikely to be that these people truly don't think disabled people feel suffering, or feel it only mildly. It must be something else.
One possibility is that many developmentally disabled people are atypical in emotional reactions to events and in how we show our emotions. I have less sympathy for people who are upset by something if it's something that I've never been bothered by (for example, a claustrophobic in a small space). I also have less sympathy for unhappy people who are harder for me to read emotionally. Not that I don't think their feelings matter, in either case. I just don't feel as strong an emotion reaction to their suffering. And this is when I do realize they're unhappy.
The solution to this is simply to recognize it and remind yourself that just because you don't feel that way or show it that way doesn't mean the person's suffering isn't as strong as yours, and to consciously try to react appropriately.
Another possible explanation is not knowing how to help. As a result, the person withdraws and shows less obvious reaction to the other person's distress. This is also cited often as a reason that bystanders don't intervene in bullying - they don't know how to. The best solution for this is education - learning how to help. If you're a parent having this kind of problem with your child, I have several bits of advice. Firstly, pay close attention to what your child likes and dislikes, and especially how they are comforted. If they rock when upset, for example, they might find you rocking them or sitting in a rocking chair comforting. Secondly, talk to other people and research stuff to find out how others deal with children like yours being upset. Lastly, try things out that you think might work, being careful to stop if it's making things worse.
Another possibility is unconscious prejudice. Although you may overtly disagree with a position, and honestly think you disagree with that position, you might on some level agree with it. This shows up in your emotional reactions and in things you say and do without thinking much about it. It may be that some people deep down don't believe that developmentally disabled people are as capable of suffering as others are, even though their conscious beliefs are quite different. The way to deal with unconscious prejudice is to recognize it in yourself. Once you've recognized it, teach yourself different patterns of reactions by recognizing a prejudice-cued reaction and consciously correcting it, and by trying out different behavior patterns. One of the biggest impediments to dealing with your own prejudice is a strong investment in viewing yourself as a 'good person'.
A third possibility is that very often developmentally disabled people are upset more often and more severely than non-disabled people. If you know someone who often cries, you are likely to get used to them crying, and react less than you would to someone crying who rarely cries. This is appropriate if they cry more often because they show their emotions more strongly, so that mild sadness results in them crying whereas another equally sad person just gets quieter.
But this usually isn't the reason developmentally disabled people, particularly autistic people, act upset more often. Instead, it's that we're under more stress in our daily lives, exposed to more upsetting, tiring, or overloading things on a day-to-day basis than most people are - simply because most people are fine with those things and our society is built around them. Add in the higher rate of trauma and abuse, meaning that developmentally disabled people are more likely to have flashbacks and experience extreme stress.
These sources of extra stress must be dealt with. It's not acceptable for disabled people to have so much more to deal with than non-disabled people. But that's going to take a lot of work, over a long period of time. It's going to take changing the world and discovering things about disabled people that are not currently known. Any closer you can get to that goal is a good thing.
In addition, people need to recognize this. They need to realize that this person they are with is going through much more every day than most people do. Not to pity them, but to take that into account - to give them more support, to avoid adding unnecessary further stress on them, and so on. And not just fleeting reminders - those only change things for a brief time, if at all.
Our suffering shouldn't be used as justification for killing us, subjecting us to harmful 'treatments', preventing the birth of people like us, or many other things it's used as justification for, but neither should it be overlooked or treated with less concern than the suffering of other people. Our suffering is not to be expected and accepted.