In short the Ada folks believe "Simply put, even the world’s most pro-woman, sex-positive, pro-consent talk about sex is likely to have negative effects on women at a technical conference."
They have a complete lack of understanding of hacker culture, take one or two relatively minor, usually unreported, incidents out of a group of 10k+ people in a weekend and us it to drum up hate and a paycheck for their founder as they push their specific agenda. There concerns are not hacker specific issues that affect women, they are the same women's issues that have been out there for years. Their "initiative" is widely rejected by women who are long term attendees at cons. And that is what defcon and others are, cons, not technical conferences.
Their choice in venue (cons) has a very low rate of incidents compared to the general population. They have caused far more incidents of things that may be considered sexual harassment as backlash for their bizarre behavior. At Chaos Communications Congress 29 this group handed out "Creeper cards" to men who in their sole judgement did something offensive. The folks at the con responded with their own form of "anti-feminist" cards. Their surprise at this response reiterates that they don't understand our culture.
If there are incidents where someone is assaulted then call the police. Someone keeps proposition you at a bar? Tell them to go away, then call the bar's security, have you ever been to a bar? With defcon, the move to the more traditional strip hotels from the AP has brought in loads of Vegas trash. Pimps, bro's, etc roam the hotel and proposition every girl there for "shopping for sex" or other pimply schemes. No girl is safe in any Vegas venue from these guys, welcome to Vegas. If Vegas trash keeps hassling you, ask the passing group of hackers for help, they will solve it for you without any expectation in return, that's our culture.