If people don't want their kids to see this stuff, then they need to install site filtering software on whatever computer the child is using at home as opposed to making it the ISPs responsibility. ISPs should not mass filter *any* content to please one group because it violates another group's rights to access that information.

From a business stand-point, any ISP that implements filtering I cutting out the whole share of customes who don't want any blockage/interruption to their internet service. In some areas, that could be financial suicide.

From a usability standpoint it's a mess too. Just imagine you're trying to do something of critical importance online (i.e. file taxes, pay bills) and, right in the middle of the process, you're blocked from accessing the next page as the ISP's filter identified the page as a "non-child-friendly" one (a.k.a. false positive). You will be upset and thus have to call customer support in order to get the problem fixed allowing this site though (a.k.a. white-listed).

The best option for this "G-Rating" system would be that if the ISP supplied some parental control software to those interested at most minimal cost (though preferably no cost if possible). Also, they should provide for some sort of instructional class or tutorial on how to effectively use the software. This way the individual user is empowered to make the choice as to what is acceptable and what is not as opposed to being at the mercy of the judgments of a third-party's filter.