It's for people to be more tolerant and to not project NT assumptions onto everyone. That seems reasonable doesn't it?
By the same token, it must be reasonable for ND people not to project ND assumptions onto everyone, mustn't it? 
But it doesn't affect them directly - I am not stopping them eating or doing what they want to do. It only affects people because I am not doing what THEY want ME to do. Surely you agree it's not a good idea, or fair, to base your contentment on whether someone else acts in the way you want them to?
Unfortunately (or not), that's the way our society operates. Someone else's behaviour has an impact on how I feel. It's how I've been socialised, perhaps. There are interesting evolutionary arguments for why a lot of co-operative socialisation has come about and the advantages it confers to further social survival.
And so I modify my behaviour, on pretty much a daily basis, because I want other people to have a nice time, or because I want to achieve a particular outcome. . There is usually a conscious or unconscious cost benefit analysis involved. How much do I want to modify my behaviour to take account of theirs? A lot of that will depend on the ultimate goal.
Equally, other people's behaviour will have an impact on me and how I feel. It's something I examine pretty regularly, because sometimes you'll decide the impact of someone's behaviour is too negative (ie being around X always makes me feel bad about myself) that the sensible thing to do is to remove yourself from that situation. Other times it might lead me to think about my own behaviour or assumptions. Again, it depends on what the end goal is. But the bottom line is that we are all constantly modifying our behaviour to try to reach an equilibrium, and understanding how our behaviour affects others.
I may not always feel that someone's response to my behaviour is rational, or the way I would respond. However, I don't think an appropriate response in that situation is 'they're stupid, I'll behave how I want regardless even if they find it negative or upsetting'. I'll try to figure out why it matters to them and proceed accordingly.
And so we're back at your assumption that because you don't think something affects a person directly, it doesn't. You're negating their emotional response because you don't think it's valid. Can you see that it's not very nice to do that?