Earlier quoted context omitted.
In regards to your last line, I feel like we do need to give people some leeway and not assume bigoted intent. Most of the things we can gig people for not implementing nowadays are only recently important in our cultural consciousness. English has traditionally shied away from using accents and one can reasonably assume that if a person signs up for my English language website, they won't be using Chinese characters…
Bias isn't the same as being bigoted. If when you find out you missed it you go "Oh, crap, you're right! We should fix that" you had a bias. If when you find out you missed it you start to defend why it's fine to not include it (not to admit you should, but maybe you don't have time/it isn't worth the cost), that's the point it's bigoted. It's the difference between making a mistake, and getting defensive that it was…
I think that definition is pretty good, but it also reveals something about the popular usage of the term "bigot".
IIUC, an underlying assumption in the parent comment is a person is at fault for not accommodating the offended party's preferred taxonomy / categories / terminology. That a person is a "bigot" if they see their system's current taxonomy as better or more appropriate.
Merriam-Webster's definition is somewhat different [0]: "a person who is obstinately or intolerantly devoted to his or her own opinions and prejudices".
Note that with MW's definition, either or both persons in that "you missed it" conversation could be labelled a bigot, depending on how obstinately they held onto their views.