I live in the Paris area (initially came as a tourist) and I've visited San Francisco. It's all a matter of where exactly you are - there are bad parts and good parts. However, the worst parts of San Francisco were definitely worse than the worst parts of Paris (where no tourist has any reason to come close to, unlike in SF where it's literally a few blocks away from major tourist attractions).

You don't see people shooting heroin literally 5 metres away from a tourist attraction in Paris (for the record - right next to the queue of tourists to get on the cable car at Powell/Market stop).

As an almost life long New Yorker it pains me, truly, to read this. People used to fear this city and that kept the “average tourist” (which includes super lovely people like my parents btw) well away from the Big Apple. Oh how I miss those days. Now any average tourist feels perfectly safe in our city and no longer fears us locals. This is not good. It’s almost like being colonized, like what happened to those poor poor Barceloni. One day they had a beautiful city (though it did smell like dog shit everywhere) and before you know it they lost it to the tourists. I fear this has already happened to Manhattan, though over here in Brooklyn we do our bit to instill the necessary respect for locals and their customs for the tourists. (Yes they come over here and look at graffiti on the wall to the great amusement of us locals.)