You could call it direct action if the amount of destruction and disruption caused by the protests/riots leads to the summit being cancelled for security reasons. You could even call it direct action if people start rioting and looting corporate franchise stores - kind of a spontaneous, autonomous redistribution of resources, dig?
I personally reject the pacifist notion that all physical conflict reinforces authority - if anything, I would say that it reinforces authority to passively stand by while an authority assaults you (whether this takes the form of a cop with a baton, or a head of state with an entire nation's economic violence and military might at his feet).
There are also more subtle/indirect results that could arguably be called "direct action" but in any case aren't purely symbolic: providing visual evidence of resistance to capitalism (or authoritarianism, etc.) which, otherwise, might appear wholly unopposed; forging stronger bonds between anarchists working together in the streets; and building tactical and strategic skills that will be valuable for future resistance.