Clarify that any other filtering is not available and is not part of our contract. Offer to cheerfuly refund their money and disconnect their account if those terms are not acceptable to them. Power comes with responsibility.
Responsibility carries with it liability.
Paul doesn't block content at all. Not selectively, not otherwise. Paul maintains a list of addresses known to have generated a specific type of content. It is offered as is, without warranty, express or implied, and is merely a list of digital identifiers. Some ISPs have AUPs for their networks which prohibit the use of their infrastructure to carry content of the type which can earn one a position on Paul's list.