Barack Obama owes his presidency in no small part to the power of rhetoric. It's too bad he doesn't appreciate the damage that loose talk can do to America's tax system, even as exploding federal deficits make revenues more important than ever.

At his Arizona State University commencement speech last Wednesday, Mr. Obama noted that ASU had refused to grant him an honorary degree, citing his lack of experience, and the controversy this had caused. He then demonstrated ASU's point by remarking, "I really thought this was much...