I wouldn't put too much weight in those kinds of comments.
This isn't just some media driven hysteria.
I think where to draw the line is this "undesirable place" business. That's highly subjective, judgemental, and can cause you to lose sight of a lot.
But I think the belief/feelings that this translates to much worse crime is just not correct. I can sympathize and agree with the idea that homeless and drug problems makes SF less desirable, but I don't think it moves the needle that much on safety and crime.
The only reason I said this, is because I was there for Miami Music Week, and they had multiple shootings two years in a row. It also has a bit of a reputation from the "cocaine cowboys" years. Honestly, the city had a bit of a "feel" to it, but it also seemed to have a great amount of character.
I'm not really passing judgement myself. I live in a place that many people would call "undesirable", and it does hurt... it's also not really fair, because it's a beautiful city with rich culture heritage, and continuing culture.
However, we have lots of shootings here too, and I understand why people are a little apprehensive.