Websites are still accessible if Google delists them.

That's akin to saying if I tore up the road leading to your house, your house is still accessible. You're not wrong, but you can't deny the power that Google has when it comes to access to websites. Furthermore, if Google started delisting some websites, you probably wouldn't even notice, which makes this all the scarier. There's a solution to be found that doesn't involve Google acting as some kind of pseudo-internet police.

At the same time, Google has a responsibility to their users. Their search engine is a list of what are likely to be the best results. If a website regularly spreads malware, is it in the best interest of Google's reputation to link to it?