I think anger is ok and justified at times, and not always just a consequence of being in the wrong state of mind, etc. I think we're more and more moving to a mindset where anger is just not really ever acceptable, either to feel or to display. But, that's all a bit heavy for what this is trying to accomplish, which is certainly an understandable goal.
Allegedly, the problem was that I hadn't apologized that they were having a bad experience with a service that we offer.