Busacca made the much criticised decision to send off Robin van Persie for kicking the ball away with the score at 1-1 on Tuesday night.
Djourou told The Sun: "I am Swiss and the referee was Swiss. I feel a sense of shame.
"He had no right to take a decision of that kind. It changed the course of the game.
"At this level of football you cannot accept decisions like that.
"But you have to admit that Barcelona deserved their win."