I've always been taught, not to hit the face.
However in these cases, it's prolly best to set an example and walk away in one piece.
Is it possible to stay out of fights completely?
As a mum I'd say, beat the crap out of his opponent, so he never looks in my baby's direction ever again. On the other hand I'm pretty sure that's not the correct attitude.
What was the fight about, does it look like it will turn into a long running thing, or have they duked it out and settled their differences???