To a lot of people, Joe Wilson deserves credit not just for speaking his mind, but for speaking theirs. "He blurted out what many other Republicans probably were thinking," one commentator put it, while Rush Limbaugh said: "I was shouting, "You're lying," throughout the speech at the television. You're lying! It's a lie! Joe Wilson simply articulated what millions of Americans were saying."
Well, not quite. However many Americans were moved to tax the President with dishonesty as they listend to the speech, it's a safe bet they expressed themselves the way Limbaugh did, in the present progressive — "You're lying." Whereas what Wilson said was "you lie," revisting a use of the simple present that parted ways with ordinary conversational English a couple of centuries ago. "You lie" — it's a sentence you expect to hear finished with "sirrah," and not the sort of thing that anyone says in a moment of spontaneous anger. (–"I really meant to put the money back." –"You lie!")
I don't mean to suggest that Wilson's effusion was planned, but it's hard to believe it was unrehearsed: it has the sound of something he had imagined himself saying to the President in numerous idle reveries, maybe as he struck a heroic pose drawn from his recreational reading:
"You lie!" Jim did not draw. He stared at Hurlburt, his eyes unwavering. Louis L'Amour, Riding for the Brand
You lie! Ben Ide is no horse thief," flashed Ina, hotly. Zane Grey, Forlorn River
But in a postmodern age, most of us associate that use of the simple present less with earnest melodrama or romance than with pastiches and send-ups of the genres. Which is why, quite independent of the generic impertinence of Wilson's remark, it sounded such a (Rocket J.) squirrely note. Limbaugh is just one of any number of people who are ready to excuse or even sympathize with Wilson's issues with impulse control, but my guess is that a lot fewer of them would want to share that particular aspect of his inner life.