Feel free to defend it, but I think that allowing low paid, overworked nursery employees to spend 8+ hours a day raising your children at the most formative point in their life, is arguably more harmful to the child than an infrequent hit on the hand or bottom in an otherwise loving, stable household. Though neither is ideal.
Personally, I think that parents should do the parenting (shocking concept, I know), and not pay others to do it for them 30 - 50 hours a week.
Plenty of people manage to raise their children with one parent staying home until they start school, or work part-time from toddlerhood until starting school, with the children only spending two days in nursery to get socialisation with other children, while still spending the majority of time with a parent.
I don't think childcare is terribly harmful, but I do wonder if people realise how hypocritical and irrational it is when they get so up in arms over the rare smack, while they send their incredibly vulnerable children off to be minded by total strangers 5 days a week during their most formative years.
People are so easily influenced by fluctuating social norms that aren't driven by what's best for the child, but rather what's convenient for the parent.