Well for one...it's not as bad as having a shoe thrown at you....
and here is when it happened:
OBAMA: "The reforms I'm proposing would not apply to those who are here illegally." One congressman, South Carolina Republican Joe Wilson, shouted "You lie!" from his seat in the House chamber when Obama made this assertion.
THE FACTS: The facts back up Obama. The House version of the health care bill explicitly prohibits spending any federal money to help illegal immigrants get health care coverage. Illegal immigrants could buy private health insurance, as many do now, but wouldn't get tax subsidies to help them. Still, Republicans say there are not sufficient citizenship verification requirements to ensure illegal immigrants are excluded from benefits they are not due.
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Fact checking Obama's speech, click to see the rest of the story