You misunderstand copyright law. The copyright on any photo is the photographer's copyright or the company employing the photographer. (It usually doesn't matter what's in the photo, though there are rare exceptions.) It doesn't matter if it's a photo of you; the photographer owns the copyright.
So when you take a photo of a photo, you are violating the photographer's copyright on the original photo.
Another misunderstanding of the law. Again, remember that the copyright is owned by the photographer. When you take a photo of something in the WWoHP, you own the copyright to that photo, not Universal. However, because you are taking photos of trademarked material, you are limited in what you can subsequently do with that photo.
I won't bore you with the details here. The main point is that taking a photo of the photos at the ride exits is indeed copyright infringement.
Disney seems to be more relaxed about enforcement. Sometimes individual CMs do something about it, sometimes they don't. But I wouldn't be surprised if they take more aggresive steps in the future.
Dave