Why, in Macbeth's opinion, is the murder of Duncan so wrong?

Macbeth ponders on a number of things that make Duncan's murder wrong. Duncan is a king, a relative, and someone Macbeth loves.... how could Duncan's murder ever be the answer.

Macbeth, until he murders the king, has always been a loyal and faithful subject to the king. Duncan was loved by nearly everyone, including Macbeth. He was kind, caring, a great king and he had ruled for many years. Because of this, Macbeth thought killing Duncan was wrong due to the fact that Duncan a good person with a big heart and had done no wrong to Macbeth.