Should it be a penalty? I'd say more obstruction, you're impeding the player getting to the ball with no intention of playing it yourself.
And to be fair, giving free kicks would have a more sensible effect into stamping it out rather than giving 12 penalties a game.
Whatever he was pulled back but let's be honest, if Skrtel was done for it next week we'd be up in arms. Ref chose the wrong game to make a point in.