Usually surveillance is something parents aren't mature enough to handle. It wouldn't be a big problem if the parents were mature enough to step back and say 'is there any actual probability of actual harm here?' Unfortunately, most parents use surveillance to actively do harm. Not intentionally, of course, but parents lack a basic understanding that change and growth in maturity and capability in their children is a GOOD thing. They typically see it as their primary responsibility to prevent their children from changing, to "protect" them against the exact experiences which are completely necessary and required to induce development. Brain development does not occur automatically. It is not a function of growth of new neurons or a function of age. It is purely a function of experience, with novel experiences and intense experiences being the primary drivers. Most parents (certainly not all, luckily) are so focused on blocking things their children aren't "ready for" that they never once stop to ask themselves what they need to do to make their child ready for the thing they're blocking.

I think that is the main sticking point people have with parents surveilling their children when concerns are expressed. Especially when doing things like reviewing all of their childs text messages, web browsing history, etc, the worry is that the parent will likely seek to moderate almost every interaction their child has with another person which is a very scary overstepping of boundaries that has never even been possible before. This rises to a level that concerns everyone in society, really, as they will be interacting with those children as they grow and when they reach a premature adulthood, having been robbed of many formative experiences 'for their own good.'