Russian Security forces attack Pussy Riot in Sochi

[ag]

Why does singing in public warrant any police action?

It is not police, BTW. These Cossacks have about as much legal existence in Russian law, as actors playing Cossacks in a theatre. Think of it as if Civil War re-enactors dressed up in grey uniforms (of their own design) and went around enforcing the Fugitive Slave Act. Wouldn´t happen even in Alabama, of course. But, naturally, this is Russia.