I'm certainly not a lawyer, but my experience is that in copyright law - for better or worse - it generally doesn't matter if you believe you have rights to use

I'm certainly not a lawyer, but my experience is that in copyright law - for better or worse - it generally doesn't matter if you believe you have rights to use some property, the only thing that really matters is if you actually have those rights. Applying that perspective CBS is absolutely in the wrong corner in that regard. As for the photographer, we don't know the circumstances of his use, but as the article noted, it's not unlikely to be considered fair use. A single frame from a movie/series can reasonably be seen as a quote, whereas their wholesale use of the photographers entire picture clearly is not. But whatever the circumstances in either case, CBS suing for a screenshot of an old movie/series seems to be a perfect way to get bad publicity, and no pity whatsoever if they would loose in court. Almost nobody wants it to be illegal/fineable to post screens and clips from TV-series, and pushing it that way is trying to get the cat back into the bag. It's part of our culture now, and that cat isn't going back anytime soon.