Sure you think you're speaking with your wallet.. but it isn't going to make any kind of an impact. You're just denying yourself something you want for no good reason.
That's wrong in general. It's a common fallacy; you're disregarding the actor.
Your own choices affect yourself. If you're denying yourself something because of principles, that changes your life. Whether or not it is for the better depends, but it actually matters a lot in and of itself.
Just because you can't heal the world in one fell swoop doesn't mean you shouldn't be decisive, loyal, honest and so on.