This is a bizarre statement. There are plenty of reasons to write software that don't revolve around "I want this software for my own personal benefit". For example the person in question may just want experience of programming, and/or they may wish to contribute to something that helps others rather than themselves.
(I suspect many people are in a similar position in their day job, given the existence of large amounts of software for which the target audience is not computer programmers.)
There's a difference between a for-profit company with a government-backed monopoly, and a not-for-profit organisation with government support (of which there are already many examples).
I don't think anyone here blames companies for putting up a paywall or doing something else to maximise their profits; it's why they exist. However, we do recognise that this is not always an ideal state of affairs. A public sector body is one way to remove the profit requirement; private-sector not-for-profit organisations are also a possibility (but have to worry more about where their funding comes from).
This is how capitalism works. Companies (and individuals) try to maximise their own profits; and (ideally) the most profitable course of action is the one which is the most beneficial to the most people. Altruism has no place in it.
And yet, people are continually surprised and disappointed when a company takes a profitable course of action, rather than ignoring profits for altruistic reasons.
In the real world, some battles are not worth fighting. Telling people that your way is correct, over and over again, doesn't necessarily mean that they'll learn, and even if you're right it doesn't necessarily win you any friends (even among people who agree with you). Sometimes you have to pick your battles and work around the incompetence, laziness, and sheer malice of others, and then vent a little to your friends, or to the internet at large if you have none.
Firstly, ranting online and confronting the problem directly are not actually mutually exclusive. Secondly, in the real world sometimes a problem just isn't worth addressing; no matter how hard you try, sales/marketing/your manager/the CEO/the users just won't understand, so just work around it and let off steam online instead.
I'm sure colourblind people would be even more "bummed out" that your design was unusable. Since, as you go on to mentioned, you don't have to sacrifice aesthetics for the sake of accessibility, I don't see why accessible design would be a problem.
While I take your point that ramps in particular aren't always appropriate, that doesn't mean that accessible design in general isn't.
But if you've only space for stairs or ramps, then you'd have to use a ramp, which everyone can use, rather than stairs, which most but not all people can use. Similarly, if you can only have one colour scheme, you ought to be picking one which everyone can read, not just most people. It's not as if it inconveniences non-colour-blind people.
> 2. Make assumptions, like that HN's readers are predominantly male. Sure, the probably are, but who knows for sure? If I was asked for my gender when I signed up, I responded randomly. Reliable demographics are simply not available.
It's well-documented that men significantly outnumber women in the software industry (and other high-tech industries). Why is it unreasonable to expect that HN reflects this imbalance? It would seem more odd for there to be an imbalance in the industry in general but perfect equality on HN.