But this is getting off topic. The point is that this particular prof for some reason does not understand the concept of seeing past the rules, and this was yet another manifestation of that mindset. He would not have canceled class unless absolutely required by the university.
And the weird thing is that he is a young assistant professor, not some old guy stuck in his ways. This makes me think that perhaps his attitude is a product of having gone through the process of getting tenure today. Maybe it turns you into a pedant (or maybe it is set up so that mostly people like him make it through, while the more laid-back among us are filtered out).