Doctors protect life, and lawyers keep you out of jail. I guess software engineers can take an oath not to kill people or put people in jail, but after that it's your morals vs. mine, no? And if I work for the Department of Defense making missile guidance software, then it's OK to kill people, I suppose...
Making missile guidance software is wholly unethical and is what we should be striving to prevent engineers from working on.
When a situation has escalated to the point that someone is launching missiles, it has usually reached the point where destroying the target is more important to them then the risk of collateral damage. If the guidance software is not good enough to give a small margin of error, they will launch several missiles to ensure that one is likely to hit the target, which pretty much guarantees a lot of damage throughout the margin of error of the guidance software.