"That's stealing. It's no different than ripping music. It's no different than pirating movies."
True. It's my computer and those are my shiny discs full of bits. Using a blocker to customize the way I interact with web pages is no more wrong than moving my music from a CD to a more-convenient file. Since blu-rays I own refuse to play on my secondary TV (an old CRT), pirating those movies gives me no moral hesitation whatsoever. Nor does turning off flash, blocking ads, or doing any of the dozens of things I do with my browsers and my other software on my computers.
If somebody wants to call what I do "stealing", well, fine. I never put my monitor up for rent as a billboard, so I could say anyone who tries to use it as such is trespassing and vandalizing my property.