They’re taking information from the page they served you and runs the code they wrote to read the page they served you to ensure what they served you is actually what you’re seeing

You’re accessing the site, you’re continuing to use the site, you are implicitly agreeing to allow the code they run to modify the page you’re on

I fail to see how it specifically being used to check that ads are displaying is any different from code running normally in your browser to change the page without refreshing the page entirely

More importantly and actually on subject: how is this immoral? What moral code are they breaking here? You can argue legal semantics, but legality is not morality. You made a moral argument. How is this immoral?

They’d argue that you going to their page which you know is sustained by ads is consent enough to check whether you’re using ad block. It’s an implicit thing, like how when you go to a restaurant you’re implying that you’re going to pay the bill afterward. You can’t eat and then leave saying, “well technically I never explicitly agreed to pay for this meal, it’s your fault for not asking before serving me.”