Macduff undergoes different emotions when Ross brings the news from Scotland concerning the massacre of his family. At first he asks, "How does my wife?" (4.3.203). Ross is not yet forthcoming and answers that all is well.
Ross is biding his time and skirting the truth to soften the blow to Macduff ("to relate the manner, / Were, ... / To add the death of you") and gives him the news of his family's destruction after gentle preparation.
Macduff's first emotion is overwhelming grief mixed with guilt. He knows it was he his rebellion against Macbeth that triggered their murders, and he did leave his family defenseless while he sought to enlist Malcolm's support and the aid of England.
When Malcolm says, "Dispute it like a man" (4.3.259), Macduff vows to get revenge on the "fiend of Scotland," and Macduff's anger and rage are apparent. This is a pivotal moment in the play because we know that only a man not born of woman can defeat Macbeth, and this man is Macduff.
How does my wife?
Why, well. ...
No; they were well at peace when I did leave 'em....
Your castle is surprised; your wife and babes
Dispute it like a man.
I shall do so;
But I must also feel it as a man:...
Bring thou this fiend of Scotland and myself;
Within my sword's length set him; if he 'scape,
Heaven forgive him too! (IV.3)