It was actually a clever and brilliant way to fill a club. Hats off! It matters not how you get them in the door, but that you get the. In the door. The club could care less how you help them to sell booze. That is why they are there. Being sanctimonious about the idea is certainly your right, but it's not getting you any further than "honesty". Nobody is going to complain to the club owner that they are a perv looking for a hookup that didn't show up, and I'm sure there weren't too many girls bothered by guys looking for hookups. Just mKe sure your girl in the ad is wearing something not likely found in a rock club like a Barry Manilow T-shirt or something. That will minimize bothering the innocent.
And who knows, a lonely guy that shows up just might actually meet a nice lonely girl....and get his groove on. And besides the entertainment industry is made up from a long serious trail of BS and lies....mistrust....abuse....backstabbing....this is just. Another tool in the ladder to actually "making it". The OP's bandmate has options...politics.. Or music promotion.