And I don't know if you've transfered domains before but I didn't have a good time doing it. Though it was not difficult I think we've seen some tremendous overstatements in this thread as to how easy it actually works out in practice.
And for me at least it's not that it not difficult to not watch ESPN. People don't live in a world without choices -- usually when they buy Battlefield they are also considering MW3 or the Batman game. There are some die-hard fans but also a lot of us that like football but are perfectly happy watching an episode or two of Breaking Bad instead if that's on. The NFL needs casual fans too, and those are the ones we should think about when we think about boycotts. Of course it will seem hopeless if you think about the guy with his face painted blue but I'm asking you to think of the guy flipping channels at home.
You only need to sway opinion a tiny little bit to change things considerably -- this is why boycotts work so damn well. The hardest thing to get over the common cynical attitude that "people won't do it, therefore we should not try."
(you should check out some Gandhi -- he explains far better than I ever can why boycotts aren't just effective but arguably the most effective tool that ordinary citizens have, and also almost always much easier to execute than we think they are)