In The Playboy of the Western World by J. M. Synge, the first indication we get of the relationship between Christy and Old Mahon is that Christy thinks he killed his father and is proud of the fact rather than remorseful. This shows that there has been a history of a bad relationship based on bullying and resentment. From the attitudes of the villagers, this appears to be socially acceptable (albeit not when it escalates to present murder). Thus I think we are getting a portrait of how abusive behaviour is passed down across generations, i.e. that Old Mahon was probably abused by his father and then replicates that model with his son. There is also a sense of an omnipresent culture of heavy drinking in the play, and thus some of Old Mahon's behaviour can be accounted for by alcohol abuse.