I haven't really decided whether I think it from a feminism point of view. The barmaid who came up with it talked about being empowered to reclaim the word, whereas local feminist campaigners made good points around the term being derogatory in almost all contexts, and some of the specific other phrases used in the marketing being taken from abusive situations.
Generally though, I think the council made the right decision partly on the basis that it's just not appropriate. There are infinite ways of describing a speed dating event with a variety of themes and implicit contexts, but 'bag a slag' is just ridiculous. I wouldn't expect them to be allowed 'pick a dick', 'gimp a pimp', 'show a hoe' or anything else to be allowed; it's a licensed venue with a responsibility to the local community, which is a very diverse one in Nottingham.