One of my buddies from my regular gaming group went to Dragon Con, and indeed there were a number of 4e games there, but they were almost entirely RPGA and mostly in their own area.
As far as the rudeness goes, I've seen some of it locally at my FLGS. Saturday night is open gaming night at the FLGS, and we have several 4e games going that night (some RPGA, some private). Earlier this summer there was a group of three guys who come by the tables every week and bitch and moan about 4e, preach the superiority of 3e/Pathfinder, heckle the players, and disrupt the game (generally being complete asshats). After several weeks of this, the staff and owner of the store asked them to leave "if you're going to behave like spoiled infants." They haven't been back...good riddance.
There is also one private PF game the same night, and these three dudes got thrown out of that game for being jackasses. Oddly enough, 4e players don't go by that table and heckle. If anything, they watch quietly, or ask questions about changes from 3e while trying to cause a minimal amount of distraction to the group.
I think the rudeness that some folks experience comes from a combination of two things: disenfranchisement from the current version of D&D, and immaturity. I can see why it would be disappointing to no longer be able to play your previous game of choice due to design decisions that make the game unenjoyable (this was the position I was in from 2003-2008 during the reign of 3e). However, I used the opportunity to explore other systems, and found some awesome other games to play! There is no reason to put down other games or attack other's opinions regarding a game- that is simply immature and small-minded. The other factor is immaturity, specifically the need to always be "right" or "vindicated". Its what I've seen time and time again in this case. These people try to preach their opinions as fact, and belittle or shout down those who disagree. There is no reasoning with them, because its become such an emotional issue and they have tied a game so closely to their identity as a person. Its immaturity and lack of social skills, pure and simple.
While there are some 4e fans who have engaged in this kind of behavior (every example I've seen has been on forums, and usually in form of sniping back at people they have had history/issues with in the edition wars), the majority of troublemakers I've seen (both in person and online) are people who feel like they have been left behind with the transition from 3e to 4e, and are dealing with it poorly. Hopefully with the release of Pathfinder (which is a good game and an improvement to 3.5, but not to my liking), they will have something to enjoy and engage in, rather than defining themselves as being "anti-4e" and agitators. We can always hope.