So much for the flip answer. I have never thought that having a conviction should be a ban for future employment. Nevertheless, the question needs to be asked, and certain convictions should be a bar to certain jobs. By not even asking the question, San Francisco is exposing itself, and its citizens, to unacceptable risks.
I wasn't trying to be flippant. I agree that you shouldn't allow people with violent pasts work with the public any more than you would allow a child molester to drive a school bus. I understand your well founded concern about liability and potential danger, I'm just pointing out that it needs to be more than a simple yes or no sort of thing.
Appropriate jobs for appropriate people. Former felons working is a lot better than former felons on welfare.