For example, it is illegal for companies to document the religious beliefs of a person BUT if this is a service for certain religious community (e.g. a forum for a church) then the term that they have to disclose their religious belief is reasonable (given that they don't share this information with anyone, of course).
As for the ads, I don't know. It might be unreasonable to have users agree to subject themselves to third-party ads in order to use the service. But again, I am not a laywer.
I'd say the TOS have to apply to the "service" you're consuming and not the website itself. Otherwise, what happens if you use just a text based browser? Or any other means not foreseen by the TOS?
An ad-blocker would be just the same, it's something that your browser does.