Intentionally running a MITM attack against your customers aside, there is a huge problem with the legislation to begin with.
Yes. The fact that no such legislation exists. This is a voluntary ISP scheme
Cybersitter and NetNanny are not for me, but if I had young kids I may use that type of service if I was worried about their access.
Or you could use the service the ISP provides you with for free, that's easy to set up, available in the UK, and works with all network connected devices.
These companies get paid to manage content for you, and are _completely_voluntary so don't impose restrictions on everyone.
The UK ISP filters are completely voluntary as well.
And if those services are not available in the UK, or not good enough in the UK, why not create the company and let the free market do the work?
We tried. No suitable product became available. David Cameron pushed the market into providing such a service. The market obliged. If you really have a problem, you can always choose one of the dozens of ISPs that doesn't offer this service.
As bad as the US has become, I'm glad I'm not from the UK.
Why? You don't even have a choice of ISP in a lot of the US.