I know this really isn't an answer but I know Crash Course has a video on it on YouTube.
Because they were viewed as property rather then people.
The correct answer is d. the justices declared the act unconstitutional because it protected against acts of private discrimination, not state discrimination
The Supreme Court ruled that the Federal government did not have the authority to prohibit private discrimination.
There is not much that they agreed on, and much of it is based on who you ask. They did however mutually agree that the US was different than other nations and that it was better.