The thing about dictators is they don’t have to answer any stinking questions from the press. We call it undemocratic; they call it job security.

That’s why President Obama’s joint news briefing with President Raúl Castro of Cuba last week was so extraordinary. For the first time since the earliest days of the revolution, independent reporters posed tough questions to a Cuban president named Castro on Cuban soil for a Cuban television audience, live. It was a moment all of us would have talked a lot more about had ISIS not intruded with mass murder in Brussels.

The first question came from Jim Acosta of CNN, whose father fled the island on the eve of the Cuban missile crisis, and he made sure the opportunity didn’t go to waste. “Why do you have Cuban political prisoners?” he asked. “And why don’t you release them?”

You could watch in real time as Mr. Castro came to terms with the idea that this was actually happening. He stammered and got himself into a muddle over how this whole news conference deal works, anyway. Was the question directed at him? It was only with prompting from President Obama that he finally answered Mr. Acosta, though by demanding a list proving that any such prisoners even existed. (Happy to help you out with that, Sir.)