Consumerism (or lack there of) is a valid way to fight bigotry or any other injustice. There is no moral or legal authority that requires that we contribute to the wealth of those that we vehemently disagree with. Money creates access, access creates influence, influence creates power. By not contributing to their wealth we diminish their power.
To simply decline the use of gay people in their ads is simply an obsolete thought of the past. Their belief is that their sales will decrease because the common media will see them as untraditional. At the end of the day its their business. But a business is only as good as the people and customers supporting it.
Occasionally, people will drive themselves into hysterics based on remarks made by an official that gets massive media attention. While the chairman of Barilla pasta's comments are deplorabe, and completely against things I believe in, if people boycotted every bigoted chairman, or every company run by people with unpopular view, they'd be surprised at how little they could buy.