Ask them to complete a questionnaire in which you ask them their opinions. For instance, are they a Democrat? Do they support President Trump? Do they support abortion? Do they support illegals being able to remain in America? If they answer the "wrong" way on any of these questions, tell them you're not interested in their business because you disagrees with their political views. Problem solved. It's legal to discriminate against others based on their political views. You're welcoem.