Hello Invictus88,
Whilst I appreciate your concern, If parental controls are set-up correctly with password protected admin and user accounts, and monitoring of the activity logs as the majority of the posters on the forum you linked to were finding. Yes there are ways of circumventing passwords, that's where monitoring is effective.
Another thing I would recommend is the use of something such as OpenDNS as the way to control site filters, if this is set in a password protected router, it adds another set of controls.
http://www.opendns.com/homenetwork/solutions/guide/
It is possible to protect children from the worst excesses of the web, it involves a proactive and interactive approach, and also involves educating younger users as to why the controls are in place