Although I have never lived in San Francisco proper, I have resided in the SF Bay Area for my entire life. There are numerous things that can contribute to such an attitude, regardless of how rude such snootiness is.
Population:
This area has one of the most diverse groups of people in the world. It is much more difficult to maintain any sort of backwater bigotry without being called on it pretty d@mn quick. The same goes for anti-semitism and homophobia too. The large scale immigration of both Asian and Hispanic people to this region automatically imposed an unavoidable degree of cosmopolitan aspect. To understand the reasons for why there is less social stratification it is necessary to examine the origins of culture as well.
Culture:
The gold rush brought to California people with incredibly diverse backgrounds. A consistent pattern among them was the willingness to take risks and respect for an individual’s labor. A sterling example is when a Confederate slave owner showed up in the gold fields. The other miners were outraged. Not at having to work with black folk as one might think back in an era of institutionalized racism. What was so irritating was that the black men did not get to profit from their labor and someone who did not work at all reaped the rewards.
Because the West was a place where people came to start their lives over, there were many ex-criminals and failed business men. It became ingrained into the culture to judge a person by their words and deeds instead of their “social standing” or background. This in turn engendered a distaste for people who relied solely on their breeding for status. For this reason this area is less socially stratified than the East coast.
Because of the gold rush, there were literally hundreds of overnight millionaires. These people, who frequently started out dirt poor, often would delegate a large portion of their wealth to acquiring the trappings of high culture. Fine houses were built on the hills of San Francisco. Famous opera singers were brought to perform. The local agriculture allowed for excellent foods to be served, and once again, the varied population made for all sorts of exotic cuisine being available.
The substantial economy that derived from the extraction of several billion (if not trillion in today’s numbers) dollars of gold from the California foothills also created its own brand of business man as well.
Business:
The gold rush mentality inculcated the participants with a proclivity for risk taking almost alien to the more staid financial institutions of the East coast. The instant accumulation of wealth made for the blossoming of large scale commercial enterprise. It is seen to this day in the entrepreneurial attitudes of Silicon Valley.
The willingness to take risks has allowed the state of California to become the economic engine of the planet. The local state economy is currently eighth in the entire world surpassing that of many industrially developed nations. This becomes a self propagating mechanism that continues to attract wealth from around the world.
Academia:
With the enormous wealth that continues to flow into this region there is a concomitant influx of educated people as well. To foster this knowledge there have been many Universities built to utilize and disseminate this learning. As the gold fields once attracted people of all backgrounds, so too do the current institutions of higher learning. The SF Bay Area specifically serves as a magnet for some of the most educated people on earth. The number of Nobel Laureates that derive from our local community is pretty much unsurpassed on a demographic basis.
Due to the overall degree of education and wide cultural base of those educated people, there is a greater degree of social tolerance for people of different faiths, creeds and orientation. This disinhibits such constraints as religious prohibitions and other overarching restrictions upon learning, behavior and attitude. Because of this atmosphere of freedom and free thinking, a level of innovation and discovery unknown to many regions of the planet finds comfortable foothold here.
All of this brings us full circle to the issues of population and culture originally mentioned at the beginning of this post. For this reason, you will often meet people who are convinced of the outstanding and often superior nature of this region. Without going into further detail, the weather and food supply also contribute to the internal perception that this area is unique to any nation on earth and remains so to this day.
If people occasionally come off as a bit smug about living here it is for well established reasons. Please remember that it remains both insolent and rude to rub someone else’s nose in it, but the feeling of satisfaction this area brings with it is undeniable.
I hope that this clarifies the encounter that you had. Please visit this area again some time so that you might gain further appreciation for the natural and cultural wonder that is the San Francisco bay area.
:eek: and SF 
:D. As has been noted, the SF area is very diverse, which means it has bigots and other maggots, too. You may just have been lucky enough to meet one.