Vatican City. That is because there aren't any 'sluts' there.
Of course, in Africa it is common for the regional 'whore' to lay on the outskirts of villages servicing anyone who arrives without showing discrimination. She never leaves and she is highly prized, not 'shamed' by anyone. That only happens when she tries to leave or live anywhere else.
Having a 'Red Light' district makes the most sense to me. That way everyone knows exactly what entering means and 'ladies' can be found everywhere else BUT the Red Light district. Choice is maintained, 'sluts' are not shamed for doing what they wish, they live in actual houses with other people, (not on roadsides), and they do their work separately from ladies. When we develop a 'universal Red Light distinct' we 'shame' women, either by trying to turn them into sluts through social pressure, or by trying to turn sluts into 'ladies' through social pressure.
That ends up being bad for everyone.