On Rosa Parks:

Parks was considered the ideal plaintiff for a test case against city and state segregation laws, as she was seen as a responsible, mature woman with a good reputation. She was securely married and employed, was regarded as possessing a quiet and dignified demeanor, and was politically savvy. King said that Parks was regarded as "one of the finest citizens of Montgomery—not one of the finest Negro citizens, but one of the finest citizens of Montgomery"

Did only finest citizens have a right to sit wherever they wanted on the bus? No. Is it smart to run a test case like this with a person who is not going to be dragged down in character assassination? Yes.