That's not the impression I got.
Button agrees, Schumacher allowed Rubens to pass on the left. One move across the track, so it's legal.
Obviously if Rubens had gone left Schumacher would probably have blocked left and made 2 moves, but he did not... he made one move to the right.
I think when Button was told that Schumacher blamed Barrichello, Button's laughter was not an indication of his agreement.