I've been on stage when there's been an inappropriate response from an audience. In one case it turned out that a phrase I used had a specific and completely unexpected meaning in that geographical area. I looked it up later, and I'm not surprised it got the response it did.

But having got that at an unexpected moment, when you're on stage in front of a large audience, working out the exact correct response can be difficult. Really difficult. To the point where you need not to respond immediately, and give it time.

I'm spoken with the author, and he's used this exact presentation in the past with a variety of audiences and had no inappropriate responses before this one. There was no a priori reason to believe this occasion would be different, and I think his response was perfectly reasonable.

You, speaking in hindsight, will have a different point of view. For me, as a speaker with over 150 engagements every year, having given presentations to various audiences for the last 25 years, I think your assessment is misguided.

Yes, there are serious issues here that need to be addressed, and no doubt there will be many self-appointed experts about what should and shouldn't be done, shown, and said. Personally, when something like this happens I think it's brave for a speaker to put in the public domain the choices made in the moment, in front of an audience, with no time to choose your words.