I'd like to respond to your post on "Ladies Nights," specifically your comment "[w]hat if a club owner wanted to attract more white patrons by offering them a special discount?"
The situation is inherently different. The goal of ladies nights is not really to attract more female customers, but to attract more male customers (who will pay full price) looking to go to bars with more female customers (for whom they will buy full-priced drinks). While we would rightly disapprove of a bar owner's catering to those who want to be around more (or exclusively) white people, I have no objection to proprietors catering to those men who are looking for a favorable female:male ratio.
I don't think adding race into the mix is totally a red herring. What if a club believed that attracting more white women would bring in more men (regardless of race) to their establishment, so it held a "White Ladies Night" with discounted drinks based on race? Non-white women could still come, and buy drinks, but just at a different price, and many of them would still get free drinks from all the extra men attracted to the club (presuming that not all of the men were only interested in white women). A counterargument could be that many non-white women lose out in the situation, thus breaking the win-win-win arrangement. But normal Ladies Night also have individuals who don't benefit: men with girlfriends or wives, gay men, or tag-along men not looking to pick up anyone.
The bars got it all wrong by offering discounts to women in order to lure them. The problem is a disparity between the genders in attendance. Why not offer half price on the second drink to those who are buying for another regardless of gender? This should up attendance.
Perhaps, although friends could just buy drinks back and forth. Any other nudge-like ideas?