>If a homeless person walks up to you and aggressively threatens you as you are passing by, no crime has occurred.

Depending on what they say, isn't that still technically "assault"? Or "disturbing the peace"?

Also, if there's poop all over the sidewalks, those are all crimes too.

The problem is that all these petty crimes are generally never reported, and certainly not acted upon by police. So they never show up in the crime statistics.

There's a disconnect between the numbers and quoted statistics and reality, because the statistics come from the police, and their reporting isn't accurate. It isn't accurate anywhere of course, because police aren't perfect and many crimes go unreported for various reasons, but to SF natives, it may seem that this is worse in SF than other places, or in SF in earlier times.