Ok i'm going to sound like a fanboy here.
But i'm not defending Barca per say here. Rather i am against the argument where you bring refs up and say they favor this team over that, especially when both teams in question are big teams. Thats why i have always argued against Arsenal, Chelsea and Liverpool fans who always claim that refs favor United in the EPL/
You see it evens itself out most of the time. Barca won by a non existant penalty today, thats true.
But go back 2 weeks, Racing Santander had a perfectly legit goal ruled out in the dying minutes against Real. It was an ever worse decision than today's one.