Ethics is not an entirely black-and-white field. If it were, there would be no room for debate and differing opinions -- we would all just do what was right or be "evil" people. But life isn't a Disney movie, and the lines are not drawn in such clear contrast.
Everything Affects Everything ElseThe problem with living a sustainable lifestyle is that we're all interconnected. None of us is really, truly self-sufficient. We rely on other people in some form or another. And those people all have their own lives and ethical dilemmas and problems. Do we buy our clothes from a major chain, which sources them from sweat shop workers? If we buy those same brands second-hand, aren't we still supporting the original purchase to some degree? If we make our own clothes, where are we sourcing our fabric from? Synthetic materials use up petroleum products, but cotton is a GMO crop. What if we only use organic cotton? Even then, it uses up so much water to produce.
And on, and on.
The deeper you delve into the question of conscious consumerism, the more complicated it starts to become. It's tempting to stop caring at all when there seems to be no perfect answer.
It's true that nobody can do everything. However, everyone can do something.
And that's really all we can ask for. Be aware of the impact you're making in the world, and strive to improve the areas that you can. Don't throw the baby out with the bathwater -- just because you can't be 100% committed to a zero-harm, zero-waste, non-consumer lifestyle doesn't mean there isn't real value in doing your best. Every dollar you spend (or don't spend) is a vote for the kind of world you want to live in, and those votes do count.