Does the play distinguish between honourable and dishonourable violence? Can this very bloody play be seen as a plea for peace and human harmony?
All is fair in love and war. In the battle scenes where the countries are at war, the "good" armies are given words with positive connotations to describe them and their actions--"worthy" "good" "honorable" and the like. This is especially true when Macbeth helps to defeat the armies in the beginning of the play for King Duncan and also when Edward, Malcolm and Macduff are gathering their forces in Act V against Macbeth.
On the other hand, the deeds that Macbeth does in secret--the murder of Duncan, the murder of Banquo, the massacre of Macduff's family--are all shadowed with bad omens (crazy stuff going on in nature like the horses breaking free of their stables and eating each other) and words with negative connotations.
It is very possible to read this play as a plea for peace and human harmony. The play begins and ends with a battle and a funeral. There are speeches given for the purpose of thanking those who are loyal and dedicated to an honorable cause. There is a period of peace after both battles, although Duncan's is very short-lived.