Moral obligation is the reason to not take/copy other things.
This is the same as music/movie piracy. Basically you're doing it because you dont have the legal/physical repercussions of taking other things in life.
Not quite - with piracy you get a modified full copy of the content from a non-original source. This non-original source produces an unlicensed copy of the content. This is the illegal or "immoral" or what have you part of piracy.
With ad blocking you go right to the original source, ask them for a copy of the content, they give it to you, then choose how you're going to render it. They gave you the content. They never made me accept a license agreement on it. I can choose to render it however I damn well please because that's up to my computer. Does IE produce an immoral rendering of the page because it doesn't support a CSS feature they use? What if I load the page in Lynx and don't see ads, is that immoral?
I kind of doubt it's even legally possible for a copyright license to only allow use if people also consume the ads linked with the content.
Might depend on your country (or state). But it doesn't really seem like a legally enforceable condition to me. Not to mention all the practical snags of such a demand.
For instance, these ads are generated real-time and are targeted towards the user. Would yielding to that be part of the same demand? If you block or shield against targeting, or even in a private tab, or clearing cookies on exit. You could make the same argument that, this too deprives publishers (part) of their income because tracking is less effective.
What if the ads contain tooling for realtime monitoring how long you are "active" on the page, which parts your mouse hovers on, etc? Are we morally obliged that we run that code and (truthfully) submit that data as well? (Rhetorical question obviously)
So if someone takes something without permission, it's ok to take it from them because they already did the original "taking"?
Morality is tied to intention. If you can only access something with a screen reader and can't see ads, that's fine. If you're intentionally removing ads while full well knowing what they are for, that's immoral.
Then again morality is subjective to the individual so perhaps this is better described as basic ethics.
This is the same as music/movie piracy. Basically you're doing it because you dont have the legal/physical repercussions of taking other things in life.