you seem to trust the news if you're asking on here.
Yes, there are homeless in San Francisco just like there are other issues related to poverty in all states blue or red. Unfortunately crime in big cities gets more attention than other bigger generational issues in the "God fearing" parts of the country.
Just keep your iPhone to yourself and look at your surroundings before using it to avoid it being grabbed. Also put your wallet in your front pocket just like it's recommended to do in Europe. Common sense!