1. People who are part of a minority by choice. For instance, they choose to use an old computer, old OS, old web browser, etc. even though it is within their means to upgrade. Or they have current software but intentionally restrict it with add-ons like NoScript. You might be justified in not catering to these minorities, because it's just not profitable and you have no moral obligation to do so. Maybe the GP falls in that category; I don't know.
2. People who are in a minority through no choice of their own, and have no power to change their circumstance. One example would be a poor student or job-seeker who's stuck with an old computer and can't do anything about it. People with disabilities also fall in this latter category. I know someone who once lost a job because he is blind and some inaccessible software barred him from doing that job. He described how that felt in this blog post:
http://blindaccessjournal.com/2006/02/torn-from-the-collecti...
All that to say that your comment is quite insensitive. Those are real people in that small minority, and depending on why they're in that minority, we developers might have an obligation to accommodate them.
EDIT: Yes, I know that JavaScript apps can be accessible.