I take it you have no idea who "pussy riot" is?
They are a Russian punk rock band who wrote songs against Putin. They have since been arrester, detained and have subsequently "disappeared".
The banner tonight was in support of them and lesbian and gay Russians who are likewise being arrested, detained , beaten up under new Russian laws outlawing gays rights, hence "free pussy riot" being written on a rainbow flag.
The banner was taken by city stewards who claimed it was offensive...before the match so if you saw it during the penalty you must have good eyesight!
The stewards also tried to take the women's tickets off them...sound a but like Russia to me!!