I fully agree that should have been a penalty. But you're missing the point. The pro-Liverpool brigade during and after the game made sure this was the main talking point after the game. They did the same last season with the so-called Azpilicueta foul on Luis Suarez. But Skrtel fouls Costa in the box in the FA cup, a blatant penalty and no one talks about it. He elbows a Chelsea player, silence. Gerrard pushes his head against Costa, it's Gerrard so it's no big deal. And there are countless examples like this, but I won't go on any longer.
Also, look at what the shameless Neil Ashton of the Daily Mail is leading with right now, it's incredible what's going on this season in particular. But you can choose to believe there isn't a campaign against us or at least an insane double standard.