Part of it, I'm sad to say, is that many, many programmers don't see themselves as professionals, but rather as mere laborers. If you try to get a doctor or a lawyer or a structural engineer to do something egregiously wrong, they'll generally know that they're crossing a line. They see themselves as having a responsibility for the human effects of their work.

Many programmers, though, will do whatever they're told, even when they know it's pointless, wasteful, or dangerous. I've read literally hundreds of stories about programmers working on something that was egregiously fucked up. But I've heard damned few stories where programmers refused to do something they thought wrong and either a) got management to back down, or b) got fired for their refusal to do something unethical.

I don't blame individuals for that. We're not trained as professionals, we don't have a professional organization that most of us join, and we therefore don't have a serious professional code of ethics. It's unreasonable to expect most people to make ethical stands alone while creating a code on the fly. But I'd love to see the situation fixed.