WASHINGTON  In what may become the most talked-about moment of President Obama’s speech to Congress on health care, Representative Joe Wilson, Republican of South Carolina, pointed his finger and shouted, “You lie!”

It was an angry retort to Mr. Obama’s statement that illegal immigrants would not benefit from proposed health care legislation. And while other points in Mr. Obama’s speech were debatable, this one was not.

The legislation approved by three House committees clearly states that only lawful residents will qualify for new health insurance subsidies. “Nothing in this subtitle,” it says, “shall allow federal payments for affordability credits on behalf of individuals who are not lawfully present in the United States.”

But Mr. Obama did repeat some assertions he had made about the proposed health care overhaul that are not so easily defended.