"Accessing the APIs to retrieve content through an entirely alternate program, unfortunately, has been deemed circumvention and the site would have a case against anyone who tried it."
I agree - programming your browser through an extension to selectively retrieve elements is probably not circumvention or exceeding authorized access.
But I think it has been shown that iterating curl from a bash script was exceeding authorized access in Weev's case. Standard HTTP GET's to which the server replies "200 OK" but after the fact was deemed to be illegal.
Hence, there is some space between Point A and Point B but it's quite mirky IMO how large that space actually is.
We know, from a copyright standpoint, for example, that it's illegal to use an extension to surround someone else's material with your own ads. So you can't add ads, but you can remove them?
I don't know if there exists a case where a site has gone after users they knew to be using blockers (it wouldn't be difficult to determine this from the logs). But it would be an interesting case, to be sure.
Do you have a cite for that?