If they HAD to do that, they should have done it as a bluff. We should have seen Dick theorizing about what exactly made Jason go off the deep end, and then have a 'of course! That's it!' sort of moment. Then, when confronting Jason, he could have bluffed him. 'I know what he said to you, Jason - what Bruce said. I listened to it. It hurt you, didn't it? But it's not too late...' That sort of stuff. It would have had much the same result, and it would have allowed the exact contents of Bruce's message to remain private until a really good writer got his hands on them. Oh, well.