Even if the actions really do nothing, they get people active and organized, so that they can take more effective actions later on.
I honestly think a lot of this criticism is people's internalized rationalization for why they themselves don't take action.
Plenty of people were hurt by the Koran burnings!
Hundreds have been injured in riots directly caused by the these provocateurs, and completely innocent people have been killed by terrorists because of them. 1)
It has also resulted in freedom of speech restrictions, a more polarized society, and less constructive dialogue about Islam.
Wrapping the Koran in bacon and setting it on fire was never meaningful criticism of religion, it was meant to incite violence. And it did!