Regardless of the law, police and other officials generally don't like it when you take photos of them, particularly when they go into action. Keep a low profile.
I think this is almost exactly wrong. The point about having a system of law that applies to all is that whether some individual or group likes it is irrelevant. If you have to scurry about and furtively take pictures from under your mac/gaberdine, then you've already admitted defeat.
If you take a photo, openly, and legally, and in doing so some officer of the law is upset, so be it. They get to be subject to the law too. If they're so upset that they behave in an illegal manner then it is up to you [not your MP/TD/Senator] to pursue the matter through the many available channels for legal remedy.
I'm not advocating shoving your lens into the face of some policeman up his eyeballs in youthful miscreants. But I don't advocate that for the same reason that I don't shove my camera in any stranger's face.
Between good manners and legal precedent, can't we find a way to pursue a legitimate goal without loosing our sense of balance?