This is quite a slippery slope. If I host a website in one country, I do not necessarily care where people access my website from. It is not like I actively provide a service to them - they just use internet (decentralised network) to access it. What if I publish a newspaper here, someone takes it where the contents are illegal, am I accountable?
It's not about "hosting a website", it's about providing services.
If you provide services, like selling a newspaper, in the UK, you need to respect their laws, or you will suffer the legal implications of not doing so.
And regarding the accountability, it refers to the fact that imgur USED TO provide services in the UK:
> We have been clear that exiting the UK does not allow an organisation to avoid responsibility for any prior infringement of data protection law, and our investigation remains ongoing.
Companies providing services outside the UK can infringe all the UK laws they want, the UK doesn't care.
But as soon as you decide to provide services in the UK, you have to follow the law. And, as they explain in the article, if you break the law, stopping to provide services in the UK will not absolve you for your past wrongdoings.
UK legal imperialism is self centered and unrealistic and undermines speech the world over.
I’m not happy with extraterritorial assertions over internet services either, but you can’t wish them away with sophistry about “we’re not providing services to them!” if you’re happy to take their money and serve them a page in exchange. That’s the definition of a business providing a service to a customer.
It’s completely absurd to say that some hobbyist would have nexus in the UK because they run a Google Adwords campaign to get some occasional pocket change from their project. Pre-Internet, it would be like going after a US magazine because someone brought home a copy from the US. Websites are not global entities by default, somehow responsible for obeying laws across nearly 200 national jurisdictions and many more state/provincial/local jurisdictions, across different languages and legal customs. Completely absurd! Who do you think you are to demand such a thing?
On the other hand, I think it would be perfectly fine to say that UK domiciled ad networks cannot put their ads on sites that violate some arbitrary standard. (An anti-freedom law to be sure, but at least it’s consistent with common international conventions.) This puts the onus on the ad network, rather than the site owner, who may not know or care who is visiting or from which country.
So you are entirely right any country can do that at any time. Most countries don't have a way to enforce it on you or your users.