How do you feel about 10 days?
On second thought, no third thought, I think the appeals court was right in sacking the case.
If the father was charged under a state statute that prohibits hitting with a child with a belt or striking a child with force that results in wounds then the sentence was just (imo).
That's not what the statute provides, though. The article on page 1 contains a link to the original text of the opinion, which in turn cites the relevant part of the relevant statute. The statute draws the line between discipline and child abuse as follows: It's not child abuse if the following two conditions are met:
(a) The force is employed with due regard for the age and size of the minor and is reasonably related to the purpose of safeguarding or promoting the welfare of the minor, including the prevention or punishment of the minor's misconduct; and
(b) The force used is not designed to cause or known to create a risk of causing substantial bodily injury, disfigurement, extreme pain or mental distress, or neurological damage.
The father's discipline, as described in the case, complies with both prongs in the statute. The father's use of force certainly did not cause any of the harm outlined in prong (b). And although you may disagree with what the father did, it was "reasonably related to the purpose of [...] punishment of the minor's misconduct." He could have done better, but I don't mind as far as legal sanctions are concerned. It's not against the law to be a less-than-perfect father -- and that's a good thing, too.