It shall be unlawful to deny any person access to or membership or participation in any multiple listing service, real estate brokers organization or other service, organization or facility relating to the business of selling or renting dwellings, or to participate or discriminate against him in the terms or conditions of such access, membership, or participation, on account of race, color, creed, religion, national origin or ancestry. [Code 1975 § 7-5.05.]