White Christians are a very nice sort of people. They will try to turn the other cheek and follow the golden rule, but even nice people have their limits. When white Christians get angry, they aren't allowed to riot, smash windows or set things on fire (like normal people). Instead they will organize a boycott against the offending party.
When people exhibit sinful behavior, white Christians will reach out to them in love, unless of course these individuals have filed paperwork with the government to become a corporation - then these people will face righteous anger, indignation and a boycott. Not only do boycotts help white Christians express their anger, they are also one of the best ways to sit in judgment of unbelievers.
With so many competing Christian boycotting organizations (many of whom may be boycotting each other), white Christians have a hard time knowing who to boycott. McDonald's? Disney? Pepsi? Also, the success of the boycott is largely dependent on how much white Christians like the company's products. White Christians are happy to boycott products they don't use but for everything else, they'd prefer to just sign a petition.