It's become common in the UK over the past decade or so. I believe they borrowed the name, and the tactic, from the German police, who have been doing it much longer:
http://de.wikipedia.org/wiki/Polizeikessel
The main objection is not so much about police violence (though that certainly happens), but that the kettle is used to discourage legitimate protests. you have a right to protest -- but if you do, the police will probably keep you pressed together on the street for 10 hours or so, in freezing temperatures, without access to food or water or toilets.
It's become common in the UK over the past decade or so. I believe they borrowed the name, and the tactic, from the German police, who have been doing it much longer: http://de.wikipedia.org/wiki/Polizeikessel
The main objection is not so much about police violence (though that certainly happens), but that the kettle is used to discourage legitimate protests. you have a right to protest -- but if you do, the police will probably keep you pressed together on the street for 10 hours or so, in freezing temperatures, without access to food or water or toilets.