They come to the conclusion that their crime numbers are reflecting underlying density differences, but then don't redo the analysis with a per-capita control? Seems like, without that, this isn't a very useful presentation.
[1] "San Francisco leads the Bay Area in attracting the most workers from outside its boundaries, with a net inflow of more than 200,000 commuters each day" https://vitalsigns.mtc.ca.gov/indicators/commute-patterns