The rights / protected classes you are talking about are equal protection issues, which fall under the 14th Amendment. (Summarized as equal protection under the law). The Supreme Court decided in 1883 that the Civil Rights Act of 1875, which prohibited private businesses from discriminating against African Americans was unconstitutional because "The Fourteenth Amendment ... is prohibitory upon the States ... Individual invasion of individual rights is not the subject matter of the amendment" -Civil Rights Cases, 109 U.S. 3 (1883)
The Civil Rights Act of 1964 ultimately achieved what the 1875 Act could not. This Act used the Legislative power to control interstate commerce to regulate businesses as oppose to the Equal Protection Clause of the 14th Amendment, and was upheld by the Supreme Court. Congress may only use the Commerce Clause when there is a significant impact upon interstate commerce.
The decision was again reaffirmed recently in the United States v. Morrison, 529 U.S. 598 (2000). This case challenged the validity of 42 U.S.C.S. § 13981, which was a law Congress enacted that provided a federal civil remedy for the victims of gender-motivated violence.
A woman that was attacked wanted the civil remedy due to her for this. The attacker did not want to pay and appealed, alleging that Congress didn't have the right to enact such a law. The Court of Appeals for the Fourth Circuit declared the law unconstitutional. They found that there was no substantial influence on commerce, so Congress could not use the commerce clause, and they also could not use the Fourteenth Amendment because of the precedent the Court established in the Civil Rights Act of 1875. The Supreme Court reviewed the case and affirmed the decision of the Fourth District.
Therefore the 14th Amendment still doesn't apply unless the conduct is considered a state action. To be a state action one of the following criteria must apply:
- The individual is employed by the government and acting as a government officer. In other words if the individual is acting in an official capacity, whether or not the conduct is authorized by law. (Gov't Officer Exception)
- If the individual/business is performing a function that has been traditionally done exclusively by the government. (Public Function Excception)
- If the government has expressly authorized, encouraged, or facilitated the unconstitutional conduct. (Entanglement Exception)
The only Amendment that applies directly to the people is the 13th Amendment, which outlaws the practice of slavery throughout the United States.