I don't like smacking. However, it is on a long list of other bad parenting behaviours that are not criminal. Poor nutrition, not giving your kids affection, ignoring them, inviting convicted criminals into your home in their presence, smoking at home with the windows closed, having all adults in a home intoxicated while you have small children. The list is long, and smacking is like that. It isn't good behaviour, but it is not bad enough to give someone a criminal record.
That is a legitimate libertarian position.
However, I don't think owning an erotic story about spanking is bad enough either, but that doesn't get the conservatives concerned about that being illegal. See they'd find it vile that I want to remove a lot of censorship about extreme consensual adult sexual material. It is strange, but some conservatives are arguing that it be legal to commit the very act on children that it is ILLEGAL to write a graphic erotic story about involving adults.
You see the law says:
"In determining, for the purposes of this Act, whether or not any publication is objectionable ... particular weight shall be given to the extent and degree to which, and the manner in which, the publication...Describes, depicts, or otherwise deals with...Physical conduct in which sexual satisfaction is derived from inflicting or suffering cruelty or pain"
So, I suspect, some conservatives are saying it is ok to actually inflict pain upon children for correction, but writing or reading or downloading a story about adults enjoying inflicting or suffering pain, should remain a crime. Libertarianz argued during the review of censorship law a few years ago that New Zealand should follow the line of the United States, which allows written free speech that includes any erotic stories for consumption by adults. David Cunliffe simply responded like a prick saying "Oh why should we follow America?" sarcastically - because the Minister of Communications can't figure out that there are many such erotic story websites on the internet that are legal in the USA and easy to access in New Zealand (you don't need help finding them), so chasing up everyone who accesses those sites (and many stories on them wouldn't be illegal) is a nonsense.
Of course Parliament voted to INCREASE penalties for producing, distributing and possessing erotic stories about sado-masochism (you see child pornography comes under objectionable, but then so do a lot of things, so nobody was keen to narrow objectionable to just child pornography, as they should've).
So you see, I'll support the smacking ban being overturned - but I wont cheer it, because I don't want to encourage the behaviour. Indeed it is the same reason why I'll support ending censorship of any written matter that isn't defamation (which isn't censorship, just compensation for damage to reputation), it simply isn't the business of the state to criminalise.