Ethical decisions in software development do not only arise when we are talking about malware or copyright infringement.
If my programs are successful, then they impact the lives of thousands or millions of people. That impact can be positive or negative. The program can make their lives better or worse–even if just in minute proportions.
Every time I make a decision about how a program behaves, I am really deciding what my users can and cannot do. If I make an input required, I am forcing them to abide by my rules. (Hopefully, it is a rule they expressed first, at least.) Conversely, if I allow partial entry, then I am allowing some licentiousness. They can get away with less rigorous work.
That makes every programming decision an ethical decision.