And so they should, within the borders of the UK.
It's illegal to own unlicensed firearms in the UK. In the US, it is legal. UK authorities can prevent ownership of firearms in the UK via penalties, prevent firms from selling firearms in the UK, and set up import controls to prevent people from importing guns bought abroad. They cannot prevent foreign companies from selling firearms abroad.
Ofcom can institute penalties for UK consumers who access illegal content, prevent firms from providing such content on UK soil, and put up firewalls to prevent people from digitally importing such content into the UK. They cannot prevent foreign companies from providing such content.
Ofcom is being lazy and is trying to offload the responsibility to foreign firms.
Safety and liberty are often at odds. Let the UK decide the balance for their citizens and let their citizens bear the benefits and costs of implementing the measures.