It all depends on what the father is beating his son for.
If he was beating his son for stealing or selling drugs or getting a young girl pregnant that he can't afford to mind then he may have deserved some licks. Also we don't know if the father has spoken to his son about whatever he is being punished for on many occasions and he just won't listen and this is a last resort.
We don't know what the licks is for and it may even serve to save the boy's life in the future especially if the licks was for the boy getting involved with crime or drugs. This could be what we call tough love, who knows?
On the other hand that incident could be classed as child abuse if the father was not doing it as a last resort and the beatings are regular and way over the top in regards to the crime the boy committed.
Does the father beat the boy regularly over the slightest issue rather than talk to him?
Does the father suspect that the boy is a horn child and is taking his frustration out on the him rather than confronting his wife/girlfriend about his suspicions?
Should he get a DNA test done to put his mind at ease?
There are so many possibilities here.