When we ask questions, such as "Which is more important, telling the truth or preventing harm?” often the context is more important. Context can be determined from factors such as time and place, the nature of the situation, other people's expectations, and the relevant history.
To understand the context, let’s assume you are a resident of Nazi Germany, in 1940. A family of Jews is hiding in your attic. The German police come searching that particular family of Jews. In such a case, preventing harm is clearly more important than telling the truth.