In Shakespeare's play Macbeth, what is shown about the role that self respect has when responding to injustice?

Focusing on a particular character who possesses self-respect and a sense of justice -- a character like Macduff -- seems like a reasonable place to begin.  Macduff, a character who seems to have a healthy level of self-respect, responds to potential injustice, at first, by simply refusing to participate in it.  He feels there is something amiss in the way that Macbeth has acquired the throne, and so he does not go to Macbeth's coronation at Scone.  Later, when invited to the Macbeths' dinner party -- the one where the ghost of Banquo shows up -- he does not respond to the invitation and fails to appear at the feast.  Seeing the way Macbeth has descended into tyranny, Macduff implores Malcolm to return to Scotland to overthrow Macbeth.  However, when Macbeth murders Macduff's family in revenge for Macduff's slights against him, Macduff's self-respect will not allow him to permit Macbeth to remain alive.  He "feel[s] it like a man," and avenges his wounded honor and heart by beheading the king.

Therefore, it seems that, in this play, self-respect necessitates that a character respond to injustice.  Early on, even when he has no proof that Macbeth has taken the throne unjustly, Macduff senses it, and he cannot allow himself to attend the coronation.  He must take a stand, however small; he cannot simply go and smile and pretend that everything is all right when it isn't.  And the stands he takes grow in size and importance when he fails to appear when bidden by his king, and when he murders Macbeth because the king's unjust behaviors have become too big to bear.