CHARLIE Sheen — the beloved star of TV’s most popular sitcom, “Two and a Half Men” — is still preaching the crackpot theory that “the official story behind 9/11 is a fraud” and demanding a new investigation. In time for this week’s eighth anniversary of the terrorist attacks on the World Trade Center and the Pentagon, Sheen has written an open letter to President Obama claiming, “9/11 has been the pretext for the systematic dismantling of our Constitution and Bill of Rights.” Sheen and his fellow conspiracy theorists also believe the “Bush/Cheney regime” and the CIA orchestrated 9/11 as a ploy to invade Iraq.