Whether you are buying things you "want" or "need," you can at least be socially responsible in your shopping. But what does it mean to be socially responsible when shopping? The Better World Handbook states "different companies manufacturing the same product can have radically different impacts on the environment, workers, businesses, and communities." Every time you make a purchase, you are essentially making a vote that says you support the actions that a particular company makes to produce it's product.
The difficult question comes into play when you are simply trying to buy a white t-shirt. For example, do you buy a white t-shirt from Wal-Mart that will be cheap (and you could use the money you saved to give to a person in need) where your money goes to one of the most socially irresponsible companies or do you buy a white t-shirt from Patagonia that will cost you considerably more yet your money goes to one of the highest rated socially responsible companies?
Though there may not be a right answer, I do think that we should at least take a look at some of the lower rated companies in question and see why they are rated so poorly. You can check out your favorite store at the responsible shopper: http://www.coopamerica.org/programs/rs/ and see how they check out. You also can purchase pocket books to carry with you during your shopping to see how products/companies check out: Shopping for a Better World and The Better World Shopping Guide. It may or may not impact you to continue shopping where you do.