> at which point it's their property

This is a big part of why the implicit deal argument doesn't really make sense. If a website sends me information then the information is on my device just like a letter, so I should be able to do what I like with it. The framing of this as an agreement between the user/publisher that we accept or reject skips over the question of whether it is even possible or moral in the first place for a website operator to try and offer an unsigned contract that removes user autonomy/rights, and whether it is moral in general for us to normalize that kind of contract.

The way that online advertising gets phrased sometimes is that you have something free that's being given to you, and consumers with ad-block are going out of their way to take more or to change the content of the webpage. But that's not really what's happening -- what's happening is that something is being given to me for free, and then the person serving that content is asking to come into my house (computer) and they're saying that they should be able to tell me what to do with the content after it's entered my house. Adblocking is the same as throwing out the spam mail from your mailbox without opening it, and anti-adblocking normalizes the idea that it's acceptable for a business to guilt or pressure people into reading junk mail.

If an industry did ever start trying to guilt people for not opening every single physical letter that was sent to them, it would be good to push back against that industry even if the industry was only trying to make a moral argument and not trying to pass laws. Some implicit contracts are so inherently invasive that they should be rejected at a conceptual level -- not merely rejected by turning down the contract, but by vocalizing, "I refuse to normalize or acknowledge the concept that a remote operator in another state has any moral claim whatsoever in any situation over what a user-agent does with information that is in my home." So we reject the concept of a website delivering content in exchange for delivering ads not because we deserve anything for free, but because we don't believe website operators have any authority (legal or moral) to set up this kind of contract, and we think it is borderline immoral/invasive for them to assert that they do. Even allowing their expectation to alter browsing behavior or treating it like a contract we have to reject gives it more legitimacy than it deserves.

It's the exact same reason why we all reject the implicit social contract where advertisers expect people to leave their volume turned all the way up for commercials, or for screen readers not to skip ads during navigation around the page to different sections. Remember that advertisers are actually the people paying for this content, and their implicit contract with users is based around actual attention -- not for allowing code to run, not for rendering the ad on the page. Advertisers have an implicit contract with us where we alter our purchasing behaviors and pay attention to their products in exchange for free content. But by and large, all of us (including anti-adblock advocates) reject that agreement and say that advertisers have no moral authority to demand that. We all kind of recognize that accepting this contract with advertisers and shaming people for walking out of the room during a TV commercial would be infringing on something vaguely sacred -- people's rights to consume content how they wish within their own homes and to pay attention to what they want to pay attention to.

But then anti-adblock advocates try to draw a line saying that it's OK for a user to ignore advertising unless a user-agent helps them. That just doesn't really make any sense, it doesn't make sense to say that pressing a button to mute a TV is morally better than having the TV press the button itself; both outcomes are exactly the same. The only place to draw that line that stands up to scrutiny is around the users "home" -- to say that once content enters their network, be it physical junk mail, or TV commercials, or online ads, users are then free to do what they wish with it even if it's to burn it and never open the envelope -- and no one has the moral authority to dictate what users do with that information or to force them to read it regardless of how much other stuff is being given away for free.