This guy is running ads provided by Google, which also supplies ads to many other web sites. And if Google is distributing malware, other ad providers probably are too.

Everyone who runs third-party ads on their site also knows that they're serving up malware. Or if they don't know, they're probably using ad blockers themselves, or they live in an isolated bubble and never met someone whose machine got infected because their kid clicked on the wrong ad.

And I'm happy to pay money for non-ad-supported sites if their services are useful to me.

That's explicitly not the situation described in his post and your comment. As you yourself quoted in your previous comment, he did try things that stopped malware from being shown on his site, but wasn't willing to take the accompanying revenue hit. I know you didn't misunderstand the situation, because that was your whole complaint! (that he knows he could remove malware but isn't willing to do so because it's more profitable to continue advertising it). This means that there _are_ ways to avoid knowingly advertising malware, and unless this guy runs every site on the Web, your rationalization for feeling no guilt is based on flawed logic.