It's the idea of both at once that's implausible. Making it more walkable would gentrify it and raise rents? Sure, I can see that. But the idea that this would also somehow increase crime? Pedestrians are much more able to see or intervene in a crime than drivers are.
Muggers and burglars travel to gentrified neighborhoods to work, because it's a completely rational thing to do.
> Pedestrians are much more able to see or intervene in a crime than drivers are.
Pedestrians are easier to watch and carefully evaluate, also, and will not always be around; you can follow a target and wait until they are safe to rob. People in cars are a mystery, and near active streets a constant one.
I wonder if using tools like https://communitycrimemap.com would help with city design.
Just off the glances I've made: Most crimes happen in easily accessible areas with clear getaway routes, almost no crimes happen at the center cul de sac of a neighbourhood.
