At the end of the day we have to live with ourselves. With our own world view, morals, and ethics.
Whether or not I personally boycott something usually makes no difference in a companies bottom line.
Case in point: as a military history enthusiast who specializes in WWII, I flat out refuse to buy a Japanese vehicle. Yes, I know Toyota pickups are assembled in Tennessee, but for me it is a matter of choice. I also understand that my actions have absolutely no affect on Toyota's bottom line.
That said, there are times that group action can bring results. Remember a few years ago the gay people had a beef with Chick Fil A's owner because he was religious? And a reverse boycott of tens of thousands of people who bought Chick Fil A food? Remember the lines of people waiting at the restaraunts around the country?