There is no linear change within capitalist culture, no rachet effect. What is gained today (wheter from the left or from the right) will not survice tomorrow or the day after. The (partial) exception are those gains made by massive (and disruptive) movements. Jim Crow will never return. But had it been 'eliminated' by polite political action, slowly gaining from the base, it would have remained a constant threat, never quite wholly suppressed.
Gradual change under capitalism is always subject to gradual undoing.
Carrol