What you say is true, but it would still be true if Facebook didn't exist. It will always be true because Internet.
The problem is a legal one, not something that facebook can simply add as a feature. (Though they do have a way to report a photo in addition to untagging it. And then you explain why that photo violates privacy laws. https://www.facebook.com/help/?faq=217091804975136#How-do-I-...)
Saying because internet here effectively becomes throwing hands in the air and saying "it makes no difference - so why bother?"