[giomasce]

Sure, I am responsible for my own actions, and buying something is an action I (can) make. Therefore I bear responsibility for the side effects of my buying actions. Not the same kind of direct responsibility of those that directly make bad actions, and I don't think I should become insane over evaluating the impact of every single thing I buy, but there's a middle ground between that and ignoring the side effect of anything you buy.

There's a better viewpoint on that, though: ignore moral responsibility, think in terms of agency. Choosing from whom you buy is one of the few ways you (as an ordinary citizen) have to make the world a little steer towards a better form of itself. My own choice alone won't change much (which is correct, otherwise we'd be in an economic dictatorship), but if many people consistently care about that capitalism will work its magic and make wonders happen.