I'll say it's a ridiculous position. How can it possibly be ethical? The owner of the server and the content has specifically told you to stop sending packets at it.
I honestly don't know how to construct an argument for this because it's so obvious to me.
It's ethical because it's a public internet. The same way you can't use the force of law to stop a homeless guy from asking you for change as you walk along a public street, you can't [shouldn't be able to] use force of law to stop a client from asking your server for data as it sits connected to a public network.
It's not unethical for a beggar to continue asking for change. It's up to the passerbys to choose whether or not they'll honor his request, but he is free to make it as long as he doesn't get out of control. Many people see the client-server relationship that exists online similarly. As the beggar can't receive anything that the giver doesn't willingly give, neither can the client receive anything the server doesn't willingly give.
It wouldn't make any sense if a guy could give the beggar change and then sue him and say that he shouldn't have gotten change because he actually wanted to use it for his lunch. The judge would say, "Well, why did you give it away? You can't just change your mind and then sue someone over it." This is also what judges should ask servers who dispense information to clients and then try to take it back.
tl;dr there's no harm in asking for data, even after someone has told you no, as long as you do so reasonably.
Is it unethical to record a TV show and skip through the ads when you watch it if the network would prefer you didn't? If you agree that it is not unethical, then merely the "content owner's" (keep in mind many things people want to scrape are factual information) saying so is not sufficient to make it ethically impermissible to scrape.
I honestly don't know how to construct an argument for this because it's so obvious to me.