I wouldn't say it's common but it does happen once in a while. We hype up the Bay Area to be a utopia for race relations, and while it is a lot better than most places in the US, there's still hate crimes out here. We had kids throwing rocks at Indian people after 9/11 because they misidentified them as Afghan, and there's still occasional attacks and vandalism on Sikh properties. The number of stupid people in this country is ridiculous
It also doesn't help that San Francisco is a disgusting city filled with the grimiest and craziest bums on Earth. The city itself is beautiful, but what's the point of having a beautiful city if there's just massive populations of insane fiends roaming the streets and public transportation ? At least in LA, they're confined to one area, but SF is so geographically small that they're highly mobile. Imagine paying damn near 4K for an apartment and having this BART psychopath just chillin at your front gate and possibly taking @%@$ there too.
Every time I hop off the Caltrain when I go to visit my friends in the city, I quickly remember why I got the hell out and moved to the suburbs. Im actually not paying any less, and there might be less things to do out here, but at least my streets are clean and fiend free. There are some homeless people out here too, but they are actually normal and respectful