A police officer who orders you to stop exercising a constitutional right has committed a federal crime (18 USC 242), worth a year in federal prison if convicted. If he threatens or uses a dangerous weapon (a TASER counts) to compel compliance with his unlawful order the penalty is enhanced to 10 years (a felony by any standard).
He can legally seize the camera incidentally to a lawful arrest but must secure it just as he must secure your wallet when taking you into custody. A police officer who has probable cause to believe the recording is evidence of a crime that would be destroyed if he does not act can seize it, but must secure a warrant afterwards in order to lawfully view it. To compel you to provide a copy requires a subpoena. To delete anything from the camera requires a court order, otherwise it is destruction of evidence. If you are recording for journalistic purposes or with intent to publish the video (even if just an upload to YouTube) the camera has additional legal protections and cannot be lawfully seized even with a warrant, though a subpoena demanding a copy of the video remains possible.
I've never been able to find anything in Washington statutes or case law that says citizen's arrests can only be made for violations of state statutes. While a simple oral directive to stop exercising a right is only a misdemeanor and does not breach the peace, a threat of a dangerous weapon is both a breach of the peace and a felony. Assaulting someone while enforcing an unlawful order is also a breach of the peace (for example, knocking a camera out of someone's hands).
The FBI has a good page on the various rights violation offenses:
http://www.fbi.gov/about-us/investigate/civilrights/federal-statutes#section242