That is your perspective. Not that of the site owner, or the internet at large, victim to any abuse somebody unkind can unleash.

Security is a bit like traffic. If you're alone in the world, you do you. But you are not alone, you have a responsibility to others, be it passers by, fellow travellers or those loved ones depending on you making it back alive.

Are you going to be binning Rust and focus purely on C++?

How so? This is just the UK. While the UK really does want to enforce this globally, they really have no enforcement power against non-UK citizens who do not reside in the UK.

Certainly it's possible (and perhaps likely!) that the EU and US will want to copycat this kind of law, but until that happens, I think your alarm is a bit of an overreaction.

Which things are expensive?

It would be much easier for me to run a small business if I didn't have to worry about the intricacies of tax law or how the various company structures affect my liability - but that's life. If you want to do various things in life, you may have certain responsibilities. Again - I don't like this particular legislation, but if your hobby is a website where others can post content you have a responsibility that the content shouldn't be illegal or harmful to others. If you can't deal with those responsibilities you can't run the website. It's no different than being required to follow health & safety regulations in an IRL business, even if it's just my 'hobby'.