OK, but if the refs are with Barca why did they let United score an offside goal on Wembley then? I mean the biggest stage of all, the greatest game, and they make a crucial mistake for United and against Barca.
Because the refs aren't for Barca. Just that they get most of their decisions because:
a) they attack a lot
b) they cheat a lot (Suarez, Neymar, Busquets)
c) they make a lot of pressure on the referee
d) they have some highly respected players, and so get double standards.
Point a) This goes for most of the top teams, if you're gonna attack a lot, you're gonna get a few extra pens in your favor. We did that during Fergie's years and Scousers cried for conspiracy. Barca does that and Madrid cries for conspiracy. Real does that and Barca cries for conspiracy, etc etc.
Point b) Our very own Ashley Young got a few pens a few seasons ago by cheating. Now imagine having a few Ashley Youngs in the team, who are actually much better at playing football...
Point c) Not exclusive to Barca (Bayern/Real do it a lot too) but Barca does it more than any other team.
Point d) Just look at the example I made, if any other player in the world (bar probably Messi) would have done what Iniesta did in Atletico match, he would have been sent off. I mean, a deliberate handball as the last man and he wasn't sent off despite that the ref awarded a pen. It was as a straightforward red card as you can ever see. But it was Iniesta so double standards. (to some degree) comparable act is when Mata this year wasn't sent off despite that he made a shock horror challenge. If it was any other player in our team, he would have been sent off, but because Mata is nice and so, he survived.
So yep, it isn't refs favoring Barca deliberately, but more a combination of you being very good (point a and d) and using some dark arts (point b and c). It served you well, so no complaints from your part, I guess.