Let the BB continue to make a stink about this. Let them be the ones who're demonstrating. Since Starbucks has made it clear about their policy and that they dont wish to be a focal point it just makes the bradys look bad, not that the bradys need any help in that area.
My suggestion is that OCers/CCers dont counter demonstrate. If you're going to be present when the BBs demonstrate just buy some coffee from Starbucks but otherwise keep a low profile and let the BBs look like the asses that they are. Laughing at them is optional.