The way to reduce this type of sexism and increase understanding is through more interaction, and not less.
Yellow and red cards may achieve segregation, but they'll also introduce fear into the mix. A man who receives one of these cards, for whatever reason, will think twice before he talks to a girl at a conference again, just as a girl who has been grabbed once at Defcon thinks twice before ever going to Defcon again.
People deal with fear and stress in funny ways. Adding one more layer of fear in a society that is already a little too afraid of the opposite sex will only backfire more in some other way.
Men who grab women do so because they're afraid to talk to them. Similarly, every time a guy says "hello" to an overly paranoid girl, she'll think that he wants to get in her pants.
You're nitpicking. My stance is that they're both fears and they'll both result in more fear, which is counterproductive to a society that is trying to reduce sexism.
In this situation, it's not incumbent on the women to educate the men. It's a bar, or a party, not a classroom. The men are being told about the problem, and need to get their act together.
Maybe the way to do it is to hold a class on sexism and behavior at defcon.
Grabbing (or touching) a woman is often the only way to get attention in a loud bar. Sometimes males do it because it is a common tactic for approaching women (no really, research shows that if you touch a woman before you speak to her, the odds of a positive reaction are better, as counter-intuitive as it may seem).
Yellow and red cards may achieve segregation, but they'll also introduce fear into the mix. A man who receives one of these cards, for whatever reason, will think twice before he talks to a girl at a conference again, just as a girl who has been grabbed once at Defcon thinks twice before ever going to Defcon again.
People deal with fear and stress in funny ways. Adding one more layer of fear in a society that is already a little too afraid of the opposite sex will only backfire more in some other way.
Men who grab women do so because they're afraid to talk to them. Similarly, every time a guy says "hello" to an overly paranoid girl, she'll think that he wants to get in her pants.