What an odd post!
Perceived fairness is absolutely fundamental to so much in our society. It's why we queue instead of all rush to the front, it's why we have a welfare system where many of us get less out than we pay in, it's why so many of us get up early to work jobs we don't enjoy in order to contribute our 'fair' share. Demeaning the idea of fairness does nobody any favours, especially vulnerable people who rely on people doing the right and fair thing.
There is a point though where the balance tips too far and we need to address this in a mature and sensible way. Not dismissing their concerns as being childish but actually looking at what is happening and why people feel the way that they do. Like it or not, many working people simply don't have access to some of the cars that people on disability benefits can access even when they're on a higher or similar income. They are essentially being taxed to subsidise someone's standard of living that will be higher than their's. Disability or no disability, this is a legitimate concern.
The issue of learning disability, life expectancy and the NHS is close to my heart as I too have a relative impacted by this. All I will say is that lots of people with learning disabilities have inherent vulnerabilities that are very difficult to tackle effectively. In our experience this will impact diet, exercise and health-care, not because the person isn't being treated fairly but sadly there is a lot of self sabotage. The amount of time, effort and money that has been spent to counteract this has been huge but ultimately it is extremely difficult to completely mitigate all of this and allow them some semblance of independence which they understandably cherish. For this reason I think it's a bad example of a lack of fairness in the system as effectively you are asking for the NHS to do the impossible in lots of cases.
You can't effectively treat someone who doesn't flag issues, doesn't turn up to appointments and won't enable treatment. You can't force someone to exercise. You can't stop an adult with learning disabilities from buying crap food and overeating.