It is designed exactly to sound reasonable, while not actually being either reasonable or justifiable. It addresses no valid problem, attains no valid goal, and so needs to be sold somehow.
Perhaps the valid problem is the public getting too close to police officers performing their duty, commonly while ostensibly filming, endangering either the police officers, or the public in the process.
Does a police officer have to worry about a legitimate journalist or honest citizen 5' away filming them while performing an arrest? No. But how exactly does the cop know the person is a legitimate journalist or honest citizen, and not an acquaintance of the person being arrested?
