Read the code of conduct for PyCon: https://us.pycon.org/2013/about/code-of-conduct/ Not specifically the lines "Sexual language and imagery is not appropriate for any conference venue" and "Remember that harassment and sexist, racist, or exclusionary jokes are not appropriate for PyCon."
Because of previous issues, the organizers of the conference went out of their way to make the line between what was and was not allowed quite explicit. They did this in order to avoid having participants claim they didn't know it would make someone uncomfortable.
I am not saying that this was a firing offense, or that everything which was said was intended as a sexual joke, but some of it crossed a CLEARLY marked line which had been communicated BEFORE the conference even began.