It is arrogant. It is also closed minded and basic/simple. I read somewhere (cannot recall which book) that we are "hard wired" to judge. That our minds have already made its judgment in less than 1 second.

Something that lingers from antiquity that used to save us in the wild when we needed to judge a situation for safety now has no real purpose and makes us make silly judgments.

I have hardly any pictures on this app because of the silly judgments. You'd think you could escape it here. That nice, optimistic side of you tries to convince you this experience would be different but no, exactly the same lol.

The arrogance of the blind hypocrites in sever denial never ceases to amaze me. I've been anti social my entire life and it's only become worse because of the odd judgments people have.

I'd hope for enlightenment for many but I'm a glass half full kind of person and I know better .

I'm not entirely clear of what you're asking, but I'll give it a shot anyway.
...judge a book by its cover...
The word that I think is causing concern is the word "judge".

If we take the sentence literally, then I don't see an issue.
Why would we judge a book in the first place? Perhaps we are considering reading the book. If that's the case, the cover might be a great way to judge the book. If the cover is well done, we might be able to determine the nature of the book; is it horror, sci-fi fantasy, autobiographical. The cover might be the best way to judge the kind of book it is. Truth might be that more effort was put into the cover than the actual writing of the book, or that the cover is completely blank with only text (certainly the case for older books), and in those cases, the cover isn't really a good representation of the actual book, but for most books these days - paperbacks, novels... - the cover usually reflects the contents of the book.

If we're taking it metaphorically - don't judge a book (people) by the cover (their appearance)...
Again, might be something to say for that as well. If a person approaches me, tidy and in clean, neat attire, with a smile and cheerful look on their face, I'm likely going to be more at ease than if approached by a disheveled person with ripped shirt, crazy eyes, bruised face and blood dripping from the knife in their hand.

Are appearance (and first impressions) the end all and be all? No, probably not. But to say that it's arrogant to quickly assess a situation, I say hog wash. People make quick assessments all the time. It's a very useful ability. I'm not saying that no one deserves a second look but quickly being able to assess a situation can certainly be an advantage.

oh, but we all do it...it's called "first impressions"...trick is to hold those first impressions tenative...

What ever labels that you want to assign to it.. I feel that at least it's inaccurate. It's part of being judgmental.

Its a defense mechanism..