Because that would be careful and tolerant riding, and letting others past when you safely can, as is required in the highway code. I think you're making far too much of imagining it's not safe to be riding in secondary there.
Sure, you have every right to own the lane if you feel you need to, but that's not what makes others lives' pleasant when it's unnecessary. Like I said earlier, you either need to ride faster to justify your use of primary (and take a stronger primary rather than this half primary), or to ride slower and go secondary. I'm currently getting the impression of aggressive cyclist asserting rights beyond what is necessary, rather than fair cyclist and tolerance.
OTOH I'd be the first to admit it's easy in hindsight, and that actually doing it yourself without the benefit of video is nowhere near so easy. I guess what I'm saying is that I'd take the lesson from this experience for future rides through here.