That seems to me a red herring. The site requires you to agree to view their ads, or not access it. The nature of the ads is irrelevant-- if they are obtrusive enough to make the viewing experience unacceptable to you, your recourse is to stop viewing the site.

A site which is public cannot restrict access to its content as such. I think you don't understand the nature of public/private space in civil law. I can go to any grocery store during operating hours, zip through the aisles, then leave without buying a blessed thing. Mind you, if I did that in a manner that was obstructing actual customers from buying groceries or I was being a jerk in general they could ban me from the store. But prior to any interaction with the grocery store, its staff, and its customers, there is no legal obligation for me to not go into the store. You can't make a store that's open to the public magically private at the same time. Either it's open for business or it's closed to the public.

A website without the requirements of logging in to see its content is the same as an open to the public grocery store. All of its resources are legally free for access. It's up to the web site's administrators to decide to block access to abusive users and bots. But if a random user comes to the site with any sort of agreement text on the index page that agreement is not a contract as the user cannot be verified nor can consent be verified either (IP logs are generally not considered sufficient to identify a user in related case law). So, you as the website owner have to figure out how to display your content and how to make sure the adverts don't interfere in the operation of your public site. It's not a legal obligation of the user to see your adverts anymore than it is the legal obligation for you to make your site public. If you don't want adblocking users then make the site PRIVATE. Otherwise, you're open for business like the grocery store. And like the grocery store, you're on the hook for jerks like me who are looking but not buying.