If an overwhelmingly large proportion of a population exhibits tendency A and a smaller group tendency B, we describe the first group as normal. It’s not a value judgement so much as it is a useful description using a word from the dictionary.
It happens to correspond to the statistical definition, and certainly that is the mathematical meaning, but in every domain outside of pure mathematics, it always implies a value judgement.
Moreover in this particular case it is not just about statistical averages, it is about social norms which were built around statistical averages. So a normality in this case it is also the rights to have social norms to be built with a respect to my needs.
Categorising a group of people as not normal has negative effects.
Yeah, they are different. But not completely different. It is hard to be understanding to a social norm, when that social norms are responsible for a life full of mornings when I want to sleep, but instead I drag myself out of the bed and kick myself to keep awake.
I mean, it is happened already, there is no way to undid damage done. It is happening now, and forgotmypw17 shows us the expected reaction to a proposition to find another way to make some people to conform with social norms even when their physiology doesn't want it. I'm not saying that his attitude is constructive, rational, or the best possible, or even acceptable, but you'll get a lot of it, if you keep saying to people "we'll find a way to make you normal".
(It is mine reaction also: who do you think you are, to believe that you are more normal than me?! To write social norms ignoring my needs? To force me to conform to that stupid social norms? To make me think that I'm lazy because I cannot wake up in the morning, I have no will because I'm sleepy till 11:00, or in some other ways inferior? It is hard to not speak my mind in that style, because I hate those norms from the school. Now I'm 40, and my hate stewed for decades.).
> Society didn’t make the day 24 hours long.
It did. Maybe 200 years ago 24 hours long day was not a society's fault, but now it is. We have electricity now and electrical lights. One could be perfectly well and functioning even at night. Just some people think that if their sleep cycle aligned with Earth's rotations, it makes them special and superior.