LOS ANGELES (Reuters) - They wore T-shirts asking “What Really Happened?,” snapped up DVDs titled “9/11; The Great Illusion,” and cheered as physicists, philosophers and terrorism experts decried the official version of the Sept. 11 attacks that shook America to its core.

Some 1,200 people gathered at a Los Angeles hotel on the weekend for what organizers billed as the largest conference on the plethora of conspiracy theories that see the 2001 attacks on Washington and New York as, at best, official negligence, and at worst an orchestrated U.S. attempt to incite world war.

“There are so many prominent people who are incredibly well-respected who have stated that the evidence is overwhelming that 9/11 was an inside job,” syndicated radio talk show host Alex Jones told a news conference.

“There are hundreds of smoking guns that people need to be made aware of,” said Jones, calling for the impeachment of President George W. Bush and charging that mainstream media had been slow to cover the growing movement of 9/11 skeptics.

The “9/11 and the Neo-Con Agenda” conference comprised two days of seminars, video presentations and talks by groups including “Scholars for 9/11 Truth,” www.infowars.com and an appearance by actor Charlie Sheen.

Note to conspiracy theorists: When Lt. Topper Harley is your big name guest speaker, your convention’s got problems.