The murderer calls Macduff a traitor because Macduff has fled to join Malcolm, the rightful heir to the throne, in trying to overthrow Macbeth. Macbeth sees Macduff's actions as a betrayal of their previous loyalty to him as king.
Because macduff fled Scotland to team up with Malcom but he does not tell his wife that i why he thinks he i a traitor , however what he WA really doing is raising an army against the Scottish forces (mcbeth)
He is a baby, not yet hatched. He also calls him a "fry", a baby fish.
A murderer; traitor; assassin; treason
Lady Macduff believes her husband is a traitor, driven mad by fear. She feels his fear led him to abandon her and their children. If Scotland was not safe for him then it was not safe for them and only a fearful man would have abandoned his family this way. She concludes he simply did not love them as even the smallest and weakest animal will fight for its children.
If by Macbeth's murderer you mean Macduff (although it wasn't murder because he killed him in a fair fight) he aligned with Malcolm the elder sun of King Duncan.
That person is called a Traitor.
Lady Macduff tells her son that his father is dead because he has fled and left them without protection, which she views as a cowardly act. She emphasizes that his father is a traitor and no longer cares for them.
A traitor
quisling
A traitor
Malcolm wants Macduff to take revenge on the murderer, who happens to be Malcolm's enemy Macbeth. In this respect, Malcolm resembles Claudius in Hamlet, who uses Laertes' desire for revenge for his own personal ends.
Murderer