Your device's battery/CPU is already being used to scan everything you ever shoot a photo of, doing AI object/face recognition, so that when you search your photos for "tree" or "airplane" or "baby" or "dog" or "George" or "Martha", it can quickly bring up images that contain the requested subject. This has been going on for years - they made a big deal about it when it was first implemented. Hashing the image will take a minute fraction of the power already being used. And those images are already being scanned as soon as they arrive on the iCloud servers (and the on-device hashing wouldn't happen except to images about to be uploaded to iCloud). If you don't want your images scanned at all, you better stop using any smartphone and any cloud storage service for photos.Using your device's battery/CPU to scan everything you ever shoot a photo of as it's about to be uploaded to be sure you're not a criminal is an obvious violation of a person's privacy.
This argument is entirely irrelevant as a point against Apple's hashing mechanism because YOU CAN ALREADY SET SOMEONE UP LIKE THIS RIGHT NOW USING AN IPHONE OR AN ANDROID PHONE - in either case, as soon as the picture is on your phone, the phone uploads it to the cloud, and the scanners that are ALREADY RUNNING IN THE CLOUD will scan the images.And it's also an easy way to set someone up. Better never leave your phone unlocked or in the hands of someone who knows your password - they can just download some of this crap to your photos collection and then close the browser leaving you none the wiser.
Apple presented a new implementation of scanning that makes it more private and harder for governments to abuse, and everyone is arguing WE DON'T WANT THIS NEW THING - well, then, you're tacitly arguing in favor of keeping the EXISTING system that is uploading your images unprotected and then scanning them in the cloud RIGHT NOW.
If you don't want ANY scanning at all, then your argument isn't with Apple, it's with the government.
Also, Apple implemented Touch ID and Face ID to make it far more likely that your phone is locked when you're not using it. And if you're handing out your password to anyone else, you're being incredibly foolish.