At a minimum, if the talk proposal was overwhelmingly compelling from a content angle, I'd have little issue with being explicit, up front and individually direct with said person about the expectations for how speakers conduct themselves.
Choosing to reject a talk from someone because of who the presenter is or how they have handled themselves in the past is completely legitimate and it is not "censorship" – a conference is a curated event and someone has the job to make sure the content fits the conference.
If you want a brogrammer conference, go start one, but don't demand that we accept that sort of crap at ours just because you think you're hot shit and can offend anyone you want because "it's funny".
Why on earth not? Part of ensuring cooperation on prisoner's dilemmas is punishment. It should be bad for your career to act like an asshole and make us all look bad.
Consider it done.
As an organizer of PyCon, this Van Horn person and any others who lack basic judgement and decency skills as well as having gained a reputation for that are not welcome to present at our conference.
Yes you do. You don't want a heavy editorial hand, but you want there to BE a hand. Wanting absolutely no judgement is a great way to let total crap in.
I guess what I'm most confused by is why a talk titled "Adding Value as a Non-Technical No Talent Ass-Clown." got accepted in the first place. Really? I know SXSW isn't a hard science conference, but that seems awfully fluffy for an event that clearly has no trouble filling seats. Maybe it's one more sign we're in a bubble...
Edit: lots of folks are picking on the second sentence above and I think taking it out of context. It was a specific reply to the idea of banning a presenter based on the notion that he "already presented a sexist presentation" -- a fact offered without support. That's just bad thinking. If the guy deserves a career ban, then make that case. Don't throw it out as a tangential point in another post.