A few friends of mine have bought houses in the gentrifying parts of port richmond over the years, and I've biked through several of the intersections in that video. Yeah parts of Kensington Ave are open air drug markets, you avoid those spots. The surrounding neighborhood is run down and pretty low income, but mostly quiet and residential. I assume SF is similar in that outside of downtown you can find a path to anywhere you want to go that avoids the most obvious dangers. Similar to the parent comment, the grocery store I walk to in west philly always has a homeless woman out front and the interactions aren't scary. She says hello to me and my dog who she recognizes and asks for change, I typically say "no but have a nice day" she says "god bless" and that's that.

Speaking as a non-parent, if I had a kid near kensington ave and they walked to school (which they mostly do) I would just tell them to walk down Frankford Ave a few blocks south, which is much less scary. Teaching kids those basic "street smarts" is one of the objectives of having "free range" kids. Although I would also add that living a little ways away from the street infamous for being a drug market is within the means of the majority of the Philadelphians, and the vast majority of the hacker news crowd.