The happy theory of business ethics is this: do the right thing and you will also maximize your long-term profit.
After all, the thinking goes, doing the right thing builds your brand, burnishes your reputation, helps you attract better staff and gives back to the community, the very community that will in turn buy from you. Do all of that and of course you'll make more money. Problem solved.
The unhappy theory of business ethics is this: you have a fiduciary responsibility to maximize profit. Period. To do anything other than that is to cheat your investors. And in a competitive world, you don't have much wiggle room here.
If you would like to believe in business ethics, the unhappy theory is a huge problem.
As the world gets more complex, as it's harder to see the long-term given the huge short-term bets that are made, as business gets less transparent ("which company made that, exactly?") and as the web of interactions makes it harder for any one person to stand up and take responsibility, the happy theory begins to fall apart. After all, if the long-term effects of a decision today can't possibly have any impact on the profit of this project (which will end in six weeks), then it's difficult to argue that maximizing profit and doing the right thing are aligned. The local store gets very little long-term profit for its good behavior if it goes out of business before the long-term arrives.
It comes down to this: only people can have ethics. Ethics, as in, doing the right thing for the community even though it might not benefit you or your company financially. Pointing to the numbers (or to the boss) is an easy refuge for someone who would like to duck the issue, but the fork in the road is really clear. You either do work you are proud of, or you work to make the maximum amount of money. (It would be nice if those overlapped every time, but they rarely do).
"I just work here" is the worst sort of ethical excuse. I'd rather work with a company filled with ethical people than try to find a company that's ethical. In fact, companies we think of as ethical got that way because ethical people made it so.
I worry that we absolve ourselves of responsibility when we talk about business ethics and corporate social responsibility. Corporations are collections of people, and we ought to insist that those people (that would be us) do the right thing. Business is too powerful for us to leave our humanity at the door of the office. It's not business, it's personal.
[I learned this lesson from my Dad. Every single day he led by example, building a career and a company based on taking personal responsibility, not on blaming the heartless, profit-focused system.]