Can dear mrs. mumsnet please explain...
... why she feels it has to be regulation?
Let's be honest here. Parents forbidding their children access to certain material are flat-out censoring. That's what censorship means. It's also their right to censor as they see fit, for they're responsible for their children, and this is one of the tools of the trade.
I'm not saying this to be controversial but to make the point just why we don't want to put up with censorship by the state. We in the western world more or less agree that it's not up to the state to decide what grown-up citizens have access to.
That, say, the IWF does indeed censor with state fiat means that it's all too easy to get people to demand to have someone else remove the badness for them, heck no, for everyone. I think that's incredibly short-sighted, regardless of why these people demanded it in the first place. Even worse, it's "voluntarily" except that it isn't. It seems expressly setup to sneak around judicial oversight and as such is an assault on the integrity of the state.
As many have already pointed out now and previously, there are perfectly viable alternatives that keep the decision to censor or not firmly in the parents' hands, on whose behalf this was to be done in the first place. All you need is a little seed money and half a clue, or you can buy those these days too, and well the intended audience is already gathered in mumsnet. Not so?
So, will mrs. Roberts pray explain why her preferences must forcibly be applied to everyone through regulation instead of through natural application of her righteous right-mindedness her compatriots obviously must share, and therefore need no regulatory assistance? Please?