Big effin' deal. Your average playground basketball game has worse taunts.
Taunting the person himself is one thing, talking about his mother like that, especially when she was ill, frankly deserved some kind of action, I wouldn't blame have blamed Zidane at all, had it not been such a violent retaliation. That being said, Zidane had to be tossed, there was no other way. But as they say, there are always two sides to every story, and it's usually only the retaliator that gets caught.
I don't know what playground you grew up on, but in Jersey City those were fighting words. If that what was said, I don't blame Zidane for retaliating. He just should have been more clever in how he went about it.