That's exactly what it is. White collar upper middle class types are more exposed to it relatively (not necessarily absolutely) in SF than in other cities. Even if the actual odds of being victim of a violent crime are lower overall they're still higher per crime and people still feel more exposed because the market shares of the various things that make up the crime pie are very different in SF than in other cities.

In Chicago, Baltimore, all those other cities techies turn up their nose at for their crime rates you might get shot in a convenience store robbery, you might get knifed by a mugger but the overwhelming majority of the violence is drug dealers and users and distributors settling scores amongst themselves (because they can't use the courts to do it for them).

Contrast with SF where the overall amount (overall or per capita) of violent crime is lower but it is much, much more concentrated toward the randomly targeted crime affecting people not already involved in activity beyond the law types of creimes meaning that your odds of getting shot in a convenience store robbery or knifed by a mugger are higher in SF than a city of equivalent violent crime rates per capita that has a more normal looking crime pie chart.