I've witnessed this behavior by liberals at parties more than once.
Miss Marple and I have noted here on FR that this is a quite common liberal quality. My latest example, of several I have encountered, is a family member attending the family Christmas dinner wearing a Dennis Kucinich t-shirt with HUGE lettering.
... or, as in my own case: my wife's ultra-uberliberal uncle arriving here last Thanksgiving, as a three-day guestl and spending virtually the entire seventy-two hours hectoring and yammering on the topic of how "George Bush stole the election of '00," and "George Bush ought to be impeached," and "you need to get more of your news from genuinely impartial web sites, like MoveOn.org," and so on, and so (endlessly) on.
Blithely, arrogantly, and non-stop... in a room full of wincing, clearly aggravated conservatives serving as his HOSTS, mind.
We won't be repeating that mistake next year.