http://en.wikipedia.org/wiki/Sex-positive_movement -- "sex-positive" is a term describing a movement meant to embrace rather than repress sexuality. The play on words of "sex-negative" refers to the opposite of sex-positive, ie., sexual repression.
OP is saying that you are sexually repressed because sex jokes make you uncomfortable. This is a good point, because dongle jokes are actually not "sexist", they are simply sexual. Men hold no exclusive territory over dick jokes, or sex jokes in general. Women can tell dick jokes too. They can also joke about vaginas (Sarah Silverman much?) and both genders can appreciate the humour EQUALLY (yay equality!). Those who don't find it funny are NOT victims of sexism-- they are victims of a shitty sense of humour.
Conferences are generally laid back environments. Of course sexist exclusionary shit that assumes conference goers are male is wrong, but making a totally non-sexist joke to your mate in a talk? Fuck that shit.
Conferences are generally professional environments, which means that some degree of strictures on behaviour is normal. Conferences that are trying to be welcoming to groups that historically have found them unwelcoming try to limit the things that make them unwelcoming. Things like 'Dongle jokes' have been identified as one of those things. The Pythonic way is 'explicit over implicit'. So, Pycon's code of conduct. Can you understand this?
