I've seen some unpleasant behavior at DSFs in many of the years since David stopped attending, and not just from fans, either... However, I've searched my memory banks, and cannot recall an instance of such behavior literally being CHEERED, except perhaps by close associates of the offenders. I certainly never have, and neither----in my observation--- has anyone of my acquaintance ---which includes some people on this forum, so with all due respect, please don't taint everyone with this gulit. Of course I've seldom spent 24 hours in any one place at the conventions, but when I'm there I pay attention.
I think what sets in with bystanders is paralysis of will--- we're all waiting for someone in charge to attend to the situation, anxious about interfering if the situation is actually not as bad as we percieve, or anxious not to provoke the offender in case the activity escalates to a threat level. So what generally ensues is stunned silence, nervous titters, eye-rolling, some complaints and walk-outs, but lacking the authority to do really anything about the problem, not even having an idea of what to do about it.
IMO, some of the trouble stems from the nature of the DS events. because of the concentration basically on one show, and the lack of barriers between a relatively small amount of fans (many of whom evolved into repeat attendees) and a shrinking pool of surviving actors (ditto.) There is a sense of intimacy and familiarity between the fans and even the actors, who all seem to feel like part of a (slightly dysfunctional) family reunion where one feels safe to say what they will, or act out, and be accepted.
Up to a point, that's part of the joy of the Fest experience. However there are good, useful, or at least harmless ways to express this pleasure, and bad, obnoxious, and potentially harmful actions. Some people take the extremes of being rude and pushy for its own sake, or out of impatience and/or exhaustion, and some are just intrusive out of simple curiosity and/or poorly-expressed concern for what they perceive as a problem. We who have been attending for years may never have been disruptive, and/or learned to roll with all the tribulations after a period of adjustment (I actually used to CRY the day after coming home the first 2 years, it was all so overwhelming, and at my age, thought I was beyond that sort of thing.)
The question is how to encourage others to take the high road,, and to enforce against the negative--- the old tricky, sticky, paradox of protecting both freedom of expression and freedom from harm.
If there had been, all along, some facet of a real committee to handle real complaints attendees have, it might have nipped some of the problem in the bud long ago. Such as it is, if there should continue to be DS conventions, we're left up to our own devices and try to enjoy what there is to enjoy, befriend those who appear to share the same values, try to help or at least listen to attendees who have an honest beef, take breaks from the convention area when it's boring or annoying or just for a change of scenery, etc.
Because it would have been sad to have been deprived of the opportunity to meet some very fine fellow fans--- great human beings I wouldn't have had the opportunity to under any other circumstances, to have fulfilled some dreams of meeting idols of my adolescence, to have seen some places I never would have gone alone.... Gotta take some of the bad with the good, that's life.