I've spent a good deal of time on Parisian public transport and have no idea what you are talking about. This includes many trips to less desirable neighbourhoods. The worst I saw was constant pickpockets. Do you care to elaborate?
From my perspective, I only care about getting from paint A to point B in a safe way that doesn't kill me. Avoiding ware zone bus stops in-between counts, since the bus stops are part of the transportation system.
Obviously I've only seen one report, but it may be that the perception of cars as being safer is incorrect.
[1] - https://www.nctr.usf.edu/wp-content/uploads/2014/12/JPT17.4_...
1) The people that die running to get the bus. Or people getting run over after exiting.
2) The increased chance of getting transmittable diseases like the Flu, or now COVID.
This sounds like a drunken brawl more than a gang fight.