Why are Referees inconsistent nowadays especially in the Champions league ?

it happens only to teams which face Barcelona starting with Chelsea in 2009 and then arsenal and real madrid this season. I really doubt in Barcelona's success. and I don't mean any insult for Barcelona but this confuses me the last Chelsea match was a crisis to football. don't know why the players of Barcelona sometimes uses dirty tricks to fool the referees they are a good team and they don't have to use these games