In Macbeth, are the reasons that Macbeth offers for killing the guards believable or realistic?

In Macbeth, Macbeth kills the guards
while the other people at his castle woe the death of Duncan.  When Macbeth rejoins the
group, he tells everyone that he killed the guards.  Macduff asks Macbeth why he felt
the need to do this, and Macbeth tells him and the others that he was compelled to act
based on his love for King Duncan.  He says that he had a storm of emotions including
fury and sadness, so he killed the guards to get revenge for the fallen king.  Keeping
in mind that the other characters obviously do not know that Macbeth is the real
murderer, Macbeth's reasons seem realistic.  In the previous Act, King Duncan honored
Macbeth for his valiant fighting on the battlefield and for his continued loyalty to
Scotland.  The others see Macbeth as an honored nobleman, so for this reason, his
actions seem realistic and believable.