Serving a page costs money. Whether a physical good is exchanged isn't particularly relevant.

>I’d just argue that ads are a blight on the web, and steal from me by deliberately and knowingly wasting my computer’s resources and attempting to serve me malware. What do we do now? Whose right not to be stolen from wins out?

Ads are a blight on and off the web, but the advertisers generally aren't trying to serve you malware (though they don't always try hard enough not to). But claiming that the ads are theft is far more of a reach then claiming ad blockers are. If you don't want ads, stop requesting pages with ads.