After conference drinks are usually pretty close nit affairs. A group leaves the conference together and arrives at the bar as a group. It's one thing to complain to the bar
management that a stranger is harassing you. It's entirely another thing to explain that someone you arrived with is a problem - here you could easily imagine getting the response "your friend, your problem", rightly or wrongly
I used to work club security for a lot of years and it happens all of the time. The people at the bar have seen it before. When the alcohol starts to flow some people can change their whole demeanor and surprise even the people that they are with. So you gently escort them out and if they become too belligerent then you have the police handle it.
It's amazing what rises to the surface for some people when they get a few drinks in them. I'd agree with the above posters and advocate the immediate handling fall to the establishment. It doesn't sound like this is a isolated incident and is likely to be an issue in the future. Being a public speaker you have to consider how you present yourself and if you behave like this it shouldn't come as a surprise if you end up being omitted from future events.
