Plaintiff posted a mock police department page on Facebook and was arrested under a state law that makes it illegal to use a computer to disrupt or impair police functions, indicted by a grand jury, and acquitted after a jury trial; plaintiff had deleted comments on the page that indicated it was fake and copied the department’s warning on its own page word for word; court says whether officers had probable cause was a difficult question, but lack of previous case afford the officers qualified immunity on First Amendment retaliation claim; court holds that officers’ televised announcement o