The developer of Maryland’s largest casino has filed a $600 million lawsuit against the racetrack operators that fought his development, claiming an extensive conspiracy to “destroy” the casino and the company’s reputation. Baltimore’s Cordish Cos. and two subsidiaries say the “illicit campaign” by the Maryland Jockey Club and the Laurel and Pimlico racetrack owners to halt its planned casino at the Arundel Mills mall cost millions in legal fees and image damage. The complaint filed in Baltimore on Tuesday levels charges of conspiracy, defamation and wrongful interference against the jockey club, track owners Penn National Gaming and MI Developments, and others. Among the charges, Cordish says his opponents — who want a casino at Laurel — twisted the truth and used a $7 million contract dispute between an Indiana racetrack and a Cordish subsidiary to defame the Baltimore company.