UPDATE 1-U.S. attorneys argue Aetna-Humana deal violates antitrust law -trial

(Adds Aetna lawyer, shares) By Diane Bartz WASHINGTON, Dec 5 (Reuters) - Attorneys for the U.S. Justice Department argued before a federal court judge on Monday that health insurer Aetna Inc's planned acquisition of Humana Inc violated antitrust law for its Medicare and Obamacare exchange businesses, kicking off a trial expected to last weeks. The Justice Department filed a lawsuit in July asking the court to stop Aetna's $34 billion deal for Humana, arguing that it would lead to