"clearly about you"
That's the point, really. There's a big difference between selling a vacuum cleaner called "Dyson" (which is "passing off" and a trademark violation) and selling a book/painting/song/etc "about" Dyson (which ought to be allowed - but who knows ...).
Remember the long-lasting case against Aqua for the "Barbie Girl" song? That was - eventually - deemed not to be a trademark violation.
However, many cases seem very unclear. We've already seen responses to this article claiming the judge was obviously right, and other responses claiming the judge was obviously wrong. To me it seems like he was right, but I wouldn't claim it's completely obvious.