One goes clubbing for the purposes of overt public exercise of one's sexual animal nature (well 99% of patrons do, some just like dancing or drugs or deafening music). People are there to show off their bodies and those of their partners if they have them. Plenty of people are there in order to advertise their availability, and it's a good bet quite a few intend to 'score'. The rules in a nightclub are, for this reason, very different from those on the street (your local red-light district partially excepted) or in a daytime workplace. Harrassment is still unacceptable, but the very definition of harrassment is different. Sex-related signals abound and they must be read and understood, and ambiguities tactfully resolved, before it is clear what behaviour is acceptable.
Technical mailing lists and websites are not sexually charged environments. Well, they *shouldn't* be.