Why do Conservatives always use "state rights" as a front for their real agenda?

America has been hearing the same line since Confederacy lost the civil war. 'State Rights' is a fairly mild sounding term, it's reality is far more radical. If the Conservative idea of state rights were ped, Jim Crow Laws would still exist in certain states; Arizona would probably be building concentration camps, various groups would be barred from education, healthcare & decent housing, and collectively America would implode due to a lack of a central authority operating as a mechanism for choosing which direction America would move in on domestic & foreign policy issues