In a parallel universe, someone might have said "You're right, it isn't accessible. That wasn't my goal, and if this ever does take off then I might have to investigate other options."
But that isn't what happened, it's a bit of a double standard, and that double standard has real consequences for some of us. The bulk of the pile-on doesn't seem to be coming from my friend, but rather from a bunch of folks criticizing him for daring to politely suggest that there's another perspective worth considering.
If your response is "because more people care about the visual design of a technically sound concept than whether it is accessible because looks matter," then I'd agree with that, and we can just leave it there without casually dismissing an entire group of real people who matter. But again, that isn't what happened here.
I wish I could post web apps I've made here without contending with the half dozen "your design sucks" comments I'd likely get. But if I got them then I'd expect them, and that frustrates me to no end.
FWIW, I'm not actually all that upset. I'm kind of used to this, actually. And I know you're just trying to explain why things are what they are, which is exactly what I'm doing. :)