Unless I'm mistaken, the city lied about the data existing in a form unusable to the hackers. That lie is, itself, giving a false sense of security to witnesses for ongoing criminal investigations. Witnesses whose data is data is accessible on a website primarily (though not exclusively) accessed by criminals.

As is described in the article, this is one of the best cases of responsible disclosure I can think of in recent memory - refuting a government lie that put at-risk people's lives in danger.