Great link. Haven't seen this one before.
Whilst I understand the need for software that restricts use of the Internet for younger kids, my feeling is that such programs are ethical to use only if the kid(s) in question are aware they are being spied on. The guardian/parent's relationship with the child needs to be totally honest in this scenario, as I have seen massive rifts between kids and their parents caused by such software. It's a trust thing. The parent may feel they cannot trust the child to surf safely, but the lack of trust is reciprocated when they realise they have been trapped.
I have found in the past that most do not object once the principle has been explained to them, that it is for their own safety/sanity etc.
My two cents!