Say I run a website. I put ads on my website to make money. I program the web site to refuse service to people who do not actually display the ads, since they make me no money.
Then I have a user come to me and say that they have a disability that makes them pathologically distractable, and they block ads the same way someone else might use a larger font size or a screen reader, in order to make it practical for them to use the web in spite of their disability. They ask that they be allowed to use their ad blocking software on my website.
Clearly it would be illegal to refuse service to a user because they were using a screen reader. Do I have to allow this person to use their ad blocking software on my website?