Two former employees of Apollo Global Management LLC acted improperly after one of them went off to form a new venture, an arbitrator decided, awarding $1.2 million to the investment firm. Apollo accused Ming Dang of stealing confidential information while he was a principal at the asset manager and passing it to Imran Siddiqui, a former senior partner who was forming a new company that could potentially compete with Apollo. Dang and Siddiqui denied the allegations.