Final answer:
Laertes is disgusted because his sister Polyneices was denied proper burial rites according to King Creon's decree in the Greek tragedy 'Antigone' by Sophocles.
Step-by-step explanation:
At the graveside of his sister, Laertes is very disgusted with the royal decree that denied his sister Polyneices the proper burial rights. This event is part of the narrative in Greek mythology and drama, specifically referenced in connection to the play 'Antigone' by Sophocles. Polyneices is considered a traitor for attacking his own city, and as punishment, Creon, the king, has decreed that Polyneices should not be buried with honor but rather left unburied as fodder for animals. This harsh decree highlights the conflict between the laws of man and the laws of the gods, as divine customs require proper burial rites for the dead. Antigone, the sister of Polyneices, defies Creon's edict out of a sense of familial duty and divine justice, which ultimately leads to tragic consequences.