In the movie, Milk, Harvey Milk organized the San-Francisco gay movement by encouraging gay people to only patron businesses that were friendly to them.
Businesses that were nice to gay people flourished. While those that weren’t floundered.
The same can be applied to today; when you spend money, you’re sending a message.
Corporations have a lot of influence in this country, so its important to buy from those that support your values and give back to the community in a valuable way.