Many bus drivers and bus cleaners, many of whom my have been black, where more than likely hurt by this action. They were probably harassed and possibly paid less. You have to look at the big picture. A boycott can only hurt the economy of an area. A good historical look at this would be quotas.
Quotas are a form of boycotting another countries goods.
By doing this you drive up the price of their good and then the price of the local good because they can sell their goods for more. This will hurt consumers as well as the other nation. That other nation now will not be able to make as much money from their exports, which in turn will lower there imports and spending from our country. This will hurt our manufacturers. So you see when you make quotas and boycotts nobody wins.