Cost nothing? His identity was and (based on his constant whining) still is football. His protest cost him millions and millions. Half the country thinks he's an unpatriotic asshole and, with the exception of Nike, nobody wants a damn thing to do with him. I don't consider his protest successful, especially when you consider virtually none of his "pie in the sky objectives" have materialized (there's a shock) and the perception being pushed by liberals in the media of his cause today.
A better question is: How is it considered anything other than ineffective?