dahs here you go with a demonstration on how to be arrogant again by pretending to speak for "anyone with command of the English language".
Not everyone has to view things the way you do. "it frankly doesn't sound right " TO YOU. That doesn't mean everyone else has to agree.
Yes, language can be defined by what people believe it to mean, but there are limits on that principle. If I say apple and you insist I must have meant banana, that doesn't fly.
In this case, my meaning was perfectly clear and I explained my word choice and the reasons behind it. In fact, I choose the word I did in order to avoid potential misunderstandings (as I explained before, the word "incredible", while perhaps technically more appropriate, can lead to incorrect connotations, while "incredulous" is far less likely to do so).
A point which he basically made himself right here. Conversely, if you say banana, it doesn't mean apple, even if that's what you had intended to say. And if you meant apple but said banana anyway, you can't expect everyone else to know what you meant and insist that "your meaning was perfectly clear."