There can't be a reasonable excuse for it. If Matarazzi had said something that made everyone go "Yep, fair enough, that's enough to make a man go for you" then you'd at least go for him, not headbutt him in the chest so there's no marks left and then stand back going "what? nossing has happened 'ere. Je suis innocent. Ou est la fromage?"

The two don't add up - Zidane lost it. No excuses. The only other way out would have been to have completely decked Matarazzi, punched and kicked him, got properly sent off and not regretted it - explaining what Matarazzi had said to him and standing up for what you did because you're not going to accept that from anyone. Zidane was a coward.