The deception is really in the URL. If I see an address ending with .jpg, I expect it to load a raw JPEG, and I have some implicit expectations following that that are being broken if the site serves HTML instead.
Also, it's actually much simpler than the discussion makes it to be. Just look at the big picture. The user wants a picture, free of irrelevant or harmful bullshit. The site promises that raw image, by means of providing what looks like a direct URL. Then, it does not deliver on the promise, serving the irrelevant and/or harmful bullshit along with the picture. It's pretty clear that one side is trying to exploit the other one.
Also, it's actually much simpler than the discussion makes it to be. Just look at the big picture. The user wants a picture, free of irrelevant or harmful bullshit. The site promises that raw image, by means of providing what looks like a direct URL. Then, it does not deliver on the promise, serving the irrelevant and/or harmful bullshit along with the picture. It's pretty clear that one side is trying to exploit the other one.