By "this particular lifestyle" he largely means not designing residential streets like highways where thousands are killed and the response is simply "Oh well, accidents happen"
Not sure how this relates at all to the context. The author of Strong Towns is against engineering design which enables drivers to drive faster at the cost of everyone else's safety. By making roads wider, clearing trees from the edges, rounding out turns, etc, it naturally pushes drivers to drive faster regardless of what the listed speed limit is.
So while speeding drivers and drink drivers are at fault, the engineers who designed a world where they can go as fast as possible are at an even greater fault. Placing highway style roads in residential areas is killing people.
