The website as it displays on your computer using your computer memory and screen and CPU is your space, not the website's. So what Banksy says is even more true.
To use your analogy, your computer is your planet. If websites don't like that their ads can't get past your customs officers, that's their problem.
And the site is voluntarily serving you their content.
Your cooking magazine argument is specious: you're not requesting the website pay your bills. The analog would be a magazine which assaults you with inserts, pop-ups, fragrance scents, a 90:10 advertising-to-copy ratio (and most of the copy is product placements), and charges you $10+ for the privilege.
Oh yeah: that's what they do. Which is why I don't buy magazines (with very rare exceptions).
To use your analogy, your computer is your planet. If websites don't like that their ads can't get past your customs officers, that's their problem.