No, UK ISPs are importing 4chan into the UK. At no point is 4chan involved in the importing of it's content. It could even be argued it's not involved in exporting it either.
It is providing content to IPs located in the UK, therefore, it's knowingly exporting content. If the user bypasses controls using VPNs or proxies, it's a different thing, but I would expect 4chan to make a reasonable effort on their side in order to prevent a sitewide block.
When a resource exists on the internet, it is available to everyone. That's how the internet works. There is no mechanism by which to exclude any given country. You can try to geolocate the IP for every individual visitor, but that's a ridiculous burden for website operators and it also doesn't even work.
Ofcom is trying to censor the entire global internet. If they want to censor the UK internet, they have much, much better tools.
They're trying to enforce extrajudicial law by way of threats and bullying instead of actually taking proactive steps to "protect" UK citizens from dangerous memes.
Ofcom has the right to censor the internet within the UK. They do not have the right to an opinion about what private entities do in other countries.
No, but it's a relatively trivial setting to block IP ranges, especially for a service the size of 4chan.
> You can try to geolocate the IP for every individual visitor, but that's a ridiculous burden for website operators and it also doesn't even work.
It's not a ridiculous burden (the ranges are easy to obtain - I did it before) and it's not expected to be 100% effective against a dedicated user because proxies exist.
This is not true. There are many steps before the content is provided to IPs in the UK, with the pertinent ones being after it reaches the ISP from the backbones.
Those people are already angry at so many things it would be hard to measure the change.