Sometimes it’s hard to explain why we need strong financial regulation — especially in an era saturated with pro-business, pro-market propaganda. So we should always be grateful when someone makes the case for regulation more compelling and easier to understand. And this week, that means offering a special shout-out to two men: Jamie Dimon and Mitt Romney. I’ll come back shortly to the troubles at JPMorgan Chase, the bank Mr. Dimon runs. First, however, let me talk about Mr. Romney, whose remarks about those troubles were so off-point that they constitute a teachable moment. Here’s what the presumptive Republican presidential...