Like Boyd said, people who live in Flint were born there, or moved there when times were good and jobs could be had. Now a lot are stuck with too little money to leave, or they have too good of a job to give up. If you have lived in the city long enough, you know when you are safe and when to be wary. If you live anywhere long enough you don't want to leave, because that means starting all over again, being a stranger in a strange place.
A lot of people are leaving when they can, to where they can. Moving farther North isn't going to help them much when they realize businesses up North are mostly seasonal. Many are moving out of state where employment is more likely. Given the condition of the economy and employment all over the nation right now, I can't say moving away is going to get anyone a better life. Many have tried turning to Military service but even they are turning people away because they cannot handle putting so many people through training all at once. Delayed enlistment, at one point that I saw it, was as much as a year for some branches.
Adding a serial stabber/killer to the mix of Flint's other nasty people isn't going to change much in people's attitude. It is scary that he has been moving state to state and may have even more victims than we know of.