Without a license, there's nothing giving you the right to visit a website, because the copyright law says so. Legally speaking, you either agree to whatever license the website has in place, or you've got no right to view its content. Of course, such a license cannot have provisions that conflict with copyright or contract law and so doctrines like the fair use applies, etc.

Of course, you could say that you can't read any license, or any privacy policy and you can't observe any unwanted behavior without first loading that website. But then again, people could build and use an extension that blocks websites and warns people of unwanted characteristics. But that's not what people are doing.

> Second, Blizzard game bots use a part of the company's codebase, where the ad blocker works solely in my own browser. They do not rely on proprietary code that belongs to someone else.

That's a weak argument. Blizzard games do not run directly over hardware, but on top of an operating system that exposes high level APIs, such as DirectX or OpenGL, being in many ways just as high-level as the browser is.