Well the alternative would be that they have chosen to take a moral stand that they expect will cost themselves and their investors money. So the explanation is pretty basic for disbelieving that story.

Why is that the only alternative? Couldn’t the consequences of this particular action in fact be a good financial decision due to negative feelings toward face detection software held by some portion of IBM’s potential customers or the general public?

I suppose so. But isn't that view a cynical one also? It's not a moral stand if it's to your benefit.

I don’t understand why it would be a problem if making a moral choice is also advantageous for other reasons. In fact, surely we should strive to arrange society in such a manner that these things align.

But we don't have such a society today. So there's a distinction between those making a sacrifice and those that are not.