Moore was actually riding slower than other riders around him, and was surprised to be pulled over by Dallas Deputy Sheriff James Westbrook. When Moore protests that he isn't doing anything wrong and asks why he's been stopped, Westbrook tells him he's going to take Moore's camera to use as evidence against the other riders in the group who were guilty of violations. Moore tells the officer he can't do that, and after Westbrook gets Moore's paperwork, he retires to his car. When he reemerges he tells Moore that he's arresting the motorcyclist for having an obscured license plate. Moore protests but it does him no good – he's booked and spends hours in jail.
In response to Dallas television station WFAA airing Moore's video, the department is launching an internal investigation into Westbrook's actions. The department did release dash-cam footage of other motorcyclists, not Moore, antagonizing patrol cars during the ride – but no one is questioning why the police were there or whether anyone at all should have been pulled over. And even though Moore himself could have been less antagonistic when he was pulled over, it appears it he may have been busted for flimsy, and perhaps unconstitutional, reasons.
Scroll down to see the footage from Moore's helmet cam. The action begins at 3:10.