An adblocker is more like taking a marker and crossing out the ads in your own personal copy of a magazine with the marker. Modification for personal use is not

An adblocker is more like taking a marker and crossing out the ads in your own personal copy of a magazine with the marker. Modification for personal use is not copyright violation. If I publish a website -- telling the users that we do not bother them with ads -- and another company then injects ads into that page, it not only violates the copyright, but it causes damage to my website's reputation, because most users aren't knowledgeable enough about the Web to understand that the ads are not put there by the publisher. It's probably even worse for websites that allow members to pay to have ads removed.