As in Chicago, there is no reason to visit the crime ridden neighborhoods in Detroit.
As for the bogus national average, I'm sure there's no crime in Podunk Iowa or Idiot falls where you're likely from.
You're correct. Is Saratoga County, NY Safe? The A+ grade means the rate of crime is much lower than the average US county. Saratoga County is in the 99th percentile for safety, meaning 1% of counties are safer and 99% of counties are more dangerous.