This is very easy to see when you consider morality to be (perhaps by definition) any process which compares competing possibilities and labels some superior to

This is very easy to see when you consider morality to be (perhaps by definition) any process which compares competing possibilities and labels some superior to others. There is an implied morality acting under any goal, because one always considers the states that achieve the goal superior to ones that do not. With humans, we can have extremely complex goals, which leave room for our morality to shift around as the context changes in subtle ways (to make exceptions to rules, for instance.) Machines tend to have very simple goals by comparison. It makes it difficult to encode any potential exceptions to the rules.