That's the story those who favor antitrust want you to believe, but it's not true. Antitrust actions historically have made markets less efficient, not more. A classic case is the breakup of Alcoa aluminum, whose "offense" was to supply aluminum to its customers at lower prices and larger quantities than any of its competitors. The breakup both raised prices and reduced quantities, making things worse for customers.

> Under mainstream economic theory, Google ought to be regulated.

Even leaving aside the concerns above, Google is not a monopoly in the sense of antitrust law. The real economic problem with Google is that its users are not its customers; users are just a resource to be exploited to maximize profits due to ads. If the government were to do anything to "fix" this, the obvious thing would be to outlaw that business model.