It shall be unlawful and an unlawful real estate practice for any person to refuse to negotiate for, enter into or perform any sale or rental of any real property, because of the race, color, religion or national origin of any party to such sale or rental, or of any member of the family of any such party, or of any person using or occupying or intending to use or occupy such real property, or of any person using or occupying any real property in the area in which such real property is located.