> Hypothetical; Suppose that this scanning program only ever did what Apple said it was going to do, look for known CSAM. Would this still be upsetting? I am trying to parse if the blow back to this announcement is rooted in the tech communities' ideal of near perfect privacy, or if instead it's a reaction to what this tech could potentially be used for.

No, because there will always be false positives, which means someone is going to be manually reviewing your photos.