Although, like the other journalists have pointed out, its expected from the police to harass, hurt or arrest you in that line of business, I disagree that it should be tolerated or been accepted in a democratic society.
If you are not obstractring the police work or endangering anyone, why should one be arrested for taking photographs in public even if they are police officers. I thought they exist to assist and protect lawfull citizens not to harm them if they are not over stepping the lines.
If I am a journalist (or anyone for that matter) should I refrain from taking a photograph by the threat of being arrested or harmed if that does not violate any laws?
If I am asked kindly it's up to me to decide to be curteous and respect the privacy of an individual and not to photograph them, like I often do with all people.
But it is not illegal to take a photograph in public and it should not lead to an arrest.

I carry a journalist ID that clearly states that police officers are to assist me to fullfill my duty. If I let the police do their job and they let me do my job, what's the matter?
Even so for a civilian that is not "protected" by such a card.

Does the goverment need to start issuing photography permits? If one can carry a gun, why not a camera?