Chattanooga had a problem a few years back with so-called "home invasions". That activity ceased when a few of the 'perps were shot dead in the process....
Although I don't consider any city safe, Chattanooga is safer than most I've been through in my extensive travels....
I liked Chatanooga when I visited about 10 years ago. Of course, I was only a visitor - but was there for three days and got a chance to really look around.
From what I could see, Chattanooga's bad area seem to be west and southwest of Missionary Ridge.