Their relationship clearly isn't a good one. With that context, and depending on the tone with which it was said (remember there were enough emotions involved

Their relationship clearly isn't a good one. With that context, and depending on the tone with which it was said (remember there were enough emotions involved to write a blog post about the slide afterwards), the question "Do you want to understand what happened during your speech?" might also be interpreted as "Do you want to sit through a personal attack?". I'm not defending his slide, but I'm also not surprised he said "No". It's possible he already understood, regretted his slide, and wanted to avoid what he perceived as a forthcoming attack. It's really hard to judge since we weren't present. I think it's clear neither of us would put that slide in our own presentations, but it nonetheless might be better not to personally attack someone in a public forum based on an incident we weren't present for. Even if he was in the wrong to say "No", attacking someone automatically puts them in the defensive and makes it harder for them to constructively evaluate criticism.