If that incident had happened by itself he wouldn't have received anything.
but if anyone watched the match, there was a good 10 mins where both teams were hitting each other during tackles and such, I thought I was about to see a fight in the world cup!
In my opinion the referee was trying to make a stop to it.
Kaka's first yellow card that happened 3 minutes earlier was well deserved and could have possibly been a red if there was a bit more to it.