A conference would be a good time to explain what being nice requires of people. It needs to be made clear that proper behaviour is required at all times when dealing with fellow developers or anyone else, whether at a conference or not. We shouldn't treat conferences special with an attitude that they should be on their best behaviour while there. Being nice and respectful should be required at all times, even when you are miles apart and communicating by email. Being rude, lewd, or insulting should have consequences. These range from ejection from a particular conference to being barred from participation in FOSS projects. These consequences can be particularly effective when applied to someone employed by a FOSS company that requires participation.
A policy is just so many words if it is not enforced. Please do not turn your back if you witness this kind of behaviour. Even if all you do is take the offender aside and explain what he did was wrong, it will help. Building a community of honor and dignity requires treating offenders properly even when their behaviour is not tolerated.