If I were to guess, I'd guess that the main filter criteria for your dinner parties is geographical; when you have a dinner party in the Bay area, you invite people who can be reasonably expected to be in the Bay area. This is not entirely independant of viewpoint - memes which are more common local to the Bay area will be magnified in such a group - but the effect of that filter on moderation viewpoints is probably pretty random (similarly, the effect of the filter of 'people who like chili' on moderation viewpoints is probably also pretty random).

So the dinner party filter exists, but it less likely to pertain to the issue at hand than the online self-selection filter.