This is pretty warped.
If we want all people to turn up with their ideas, we have to create an environment where all people feel comfortable being present and expressing their ideas. We have mainly done that for white dudes with reasonable levels of social capital. I'd like to do it for everybody.
The feeling of being a visibly different minority in a crowd can be unsettling. (As a white guy I experience it rarely, but when it happens, I notice the difference acutely.) This is true regardless of actual risk. But women are currently at higher risk of all sorts of predatory behavior: creeps, stalkers, harassers, sexual assaulters, rapists. I personally expect that a sexualized environment will increase those risks. But even if they don't, suddenly having your context shifted from, "professional who likes to code thinking about code" to "fuckable prey for the predators in the crowd around you" is problematic.
Our choices are either to give up and have those people mainly stay away or to work on creating a safe space so that everybody can attend. There is no middle path here. Pycon explicitly chose the latter.
Does this exclude ideas? I guess, in a sad and limited sense of the term "ideas". Pycon's limited the acceptable content thusly: "All communication should be appropriate for a professional audience including people of many different backgrounds. Sexual language and imagery is not appropriate for any conference venue, including talks."
Does this mean you can't talk about your favorite masturbation techniques on stage? Sure. But seriously, why would you? What sort of incredible idea exchange are we missing out on here by saying that a Python conference has to be about Python? If you also want to talk about sex, there are conferences about that. There's even a well-established conference about sex and technology. [1]
What you're refusing to connect here is what happened to Adria before and after she posted a tweet about a Code of Conduct violation. She was harassed and threatened; her employer was attacked, harming their business. These are all crimes, and they're crimes for a reason. You might not see the connection, but to me (and I'm sure to any woman in tech) it's pretty obvious: men willing to attack women are part of the tech community. They could be anybody. [2]
She surely knew that there could well be predators in that crowd. And the moment the context is sexualized is the moment that she has to start paying attention to that rather than the content. This is true for anybody, but it is especially true for people who have been traumatized in the past. And given the stats on sexual assault, there are guaranteed to be women like that at any significant conference.
So I'm firmly on the side of codes of conduct because I don't want a random grab-bag of ideas at a conference. I want a specific curated set of good ideas. And if that means people have to save their weak sex jokes and their pictures of porn stars for a few hours until they're somewhere else, I'm fine with that.
[1] http://www.monochrom.at/arse-elektronika/
[2] This basically makes you and me and any dude in a crowd Schroedinger's Rapist: http://kateharding.net/2009/10/08/guest-blogger-starling-sch... http://geekfeminism.wikia.com/wiki/Schr%C3%B6dinger%27s_Rapi...