Final answer:
Tony is violating the Civil Rights Act of 1964 by refusing to show his house to potential buyers based on their religion, as the act prohibits any form of religious discrimination in business transactions.
Step-by-step explanation:
Tony's practice of asking potential buyers about their religion and refusing to show his house based on the differences in religious beliefs would violate the Civil Rights Act of 1964, which prohibits discrimination on the basis of religion in any business that is open to the public. This legislation is very clear in prohibiting any form of religious discrimination including in matters of housing. Despite the fact that individuals are entitled to hold personal beliefs, when conducting business such as selling a house, the law requires equal treatment of all persons regardless of their religion.