In what ways were the little rock desegregation and rosa parks defiance on a montgomery bus turning points in the struggle for civil rights

These were instances of "Civil Disobedience" and later "Jury Nullification" to rebel against tyranny. Without these constitutional actions, either the movement for equal rights would turn to violent bloodshed without purpose or would be suppressed into submission. To further explain, these were instances whereas the people sought to free themselves from the tyranny that was the Jim Crow laws. Even if they had enough support, they needed to prove the laws null, in court, and treat them as they are, void, in public.